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View Test Prep - Ch1 Test Bank for The Immune System 4th Edition by Parham.docx from IMMUNO 5002 at National Taiwan University. THE IMMUNE SYSTEM, FOURTH EDITION CHAPTER 1: ELEMENTS OF THE IMMUNE. Ch1 Test Bank for The Immune System 4th Edition by Parham.docx. Download the iOS. The Immune System Peter Parham 3rd Edition Pdf [READ] The Immune System Peter Parham 3rd Edition Pdf.pdf How the Immune System Works Kindle edition by Lauren M December 1st, 2018 - Buy How the Immune System Works Read 73 Kindle Store Reviews Amazon com Complement system Wikipedia December 15th, 2018 - The complement system is a part of the.
The highly polymorphic human leukocyte antigen (HLA) class I molecules present peptide antigens to CD8+ T cells, inducing immunity against infections and cancers. Quality control mediated by peptide loading complex (PLC) components is expected to ensure the cell surface expression of stable peptide-HLA class I complexes. This is exemplified by HLA-B.08:01 in primary human lymphocytes, with both expression level and half-life at the high end of the measured HLA-B expression and stability hierarchies. Conversely, low expression on lymphocytes is measured for three HLA-B allotypes that bind peptides with proline at position 2, which are disfavored by the transporter associated with antigen processing. Surprisingly, these lymphocyte-specific expression and stability differences become reversed or altered in monocytes, which display larger intracellular pools of HLA class I than lymphocytes. Together, the findings indicate that allele and cell-dependent variations in antigen acquisition pathways influence HLA-B surface expression levels, half-lives and receptivity to exogenous antigens.
The highly polymorphic human leukocyte antigen (HLA) class I molecules present peptide antigens to CD8 + T cells, inducing immunity against infections and cancers. Quality control mediated by peptide loading complex (PLC) components is expected to ensure the cell surface expression of stable peptide-HLA class I complexes. This is exemplified by HLA-B.08:01 in primary human lymphocytes, with both expression level and half-life at the high end of the measured HLA-B expression and stability hierarchies. Conversely, low expression on lymphocytes is measured for three HLA-B allotypes that bind peptides with proline at position 2, which are disfavored by the transporter associated with antigen processing.
Surprisingly, these lymphocyte-specific expression and stability differences become reversed or altered in monocytes, which display larger intracellular pools of HLA class I than lymphocytes. Together, the findings indicate that allele and cell-dependent variations in antigen acquisition pathways influence HLA-B surface expression levels, half-lives and receptivity to exogenous antigens.
Most cells in the body make proteins called human leukocyte antigen class I (or HLA-I). These proteins sit on the cell surface, where they help the immune system distinguish between healthy and diseased cells. A groove in each HLA-I protein holds a fragment of a protein chain, called a peptide, from inside the cell. In healthy cells, all the peptides come from normal proteins. Yet in diseased or infected cells, the peptides may come from abnormal or foreign proteins – those encoded by viruses, for example. When the immune system sees these abnormal peptides, it responds by killing the cell.
Across the human population, there are thousands of types of HLA-I, each able to carry a different set of peptides. Any individual person can only make a maximum of six types of the HLA-I, meaning we each show a different combination of peptides to our immune cells.
This difference will change the way different people respond to the same disease. Before a peptide can be assembled into HLA-I, it must be moved to the correct part of the cell by a transporter known as TAP. This transport favors peptides with certain characteristics, but these characteristics do not always match the preferences of the individual's HLA-I proteins. For example, TAP is less likely to transport peptides where the second building block in the chain is a proline, but these peptides will still fit into the binding grooves of some HLA-I variants. Here, Yarzabek, Zaitouna, Olson et al.
Obtained blood from healthy human donors to answer questions about what happens when TAP and HLA-I have different preferences. Specifically, how many HLA-I molecules reach the surface, how long do they last, and which peptides do they carry? This analysis revealed that, when there was a mismatch between HLA-I and TAP, the amount of some HLA-I types on the surface of white blood cells called lymphocytes dropped. These HLA-I types were also able to pick up new peptides from their environment, indicating that some HLA-I were at the surface of the cell without a peptide. The role of these empty HLA-I remains to be fully defined.
The reverse was true for other white blood cells called monocytes; HLA-I variants that were mismatched with TAP became more abundant on the cell surface. Monocytes also had more HLA-I molecules inside and did not pick up peptides from the environment. This suggests that monocytes may load peptides via new pathways, filling grooves left empty in lymphocytes, although other mechanisms might also explain the differences between the two types of white blood cells. Taken together, the findings reveal that HLA-I on the surface of cells depends on both the type of HLA-I and the type of immune cell. HLA-I proteins play a key role in the immune system’s ability to recognize and kill diseased cells.
A better knowledge of how HLA-I variants differ could help us to understand why people respond differently to the same disease. A better grasp of HLA-I could in the future lead to improved drug and vaccine design. Introduction Major histocompatibility complex (MHC) class I proteins are cell surface proteins that control immune responses by CD8 + T cells and natural killer (NK) cells. MHC class I proteins are comprised of a heavy chain, a light chain, β2-microglobulin (β2m), and a short peptide that is bound to a peptide-binding groove in the heavy chain.
Heavy chains of human MHC molecules (human leukocyte antigens (HLA)) are encoded by three sets of genes, which are the HLA-A, HLA-B and HLA-C genes. These genes are highly polymorphic, with about 5000 known alleles in the case of HLA-B and fewer alleles in the case of HLA-A and HLA-C genes.
Polymorphic residues are localized to the peptide-binding groove of HLA class I proteins and determine their specificities for peptide binding. T cell receptors (TCR) of cytotoxic T cells have specificities for combinations of MHC class I and peptide.
Binding of a CD8 + T cell TCR to peptide-MHC class I complexes triggers CD8 + T cell cytokine production and cytotoxic activity. Conversely, NK cells have inhibitory receptors that recognize HLA class I.
Engagement of MHC class I by NK cell inhibitory receptors suppresses NK cell activity. NK cell activity is induced by MHC class I down-modulation, a strategy frequently used by viruses and cancers to evade CD8 + T cell responses. MHC class I assembly involves a complex pathway that is initiated by the formation of chaperone-guided heterodimers of heavy chains and β2m. In the absence of a peptide ligand, heavy chain-β2m heterodimers are generally unstable and retained in the endoplasmic reticulum (ER) via the peptide loading complex (PLC).
The PLC facilitates peptide loading of MHC class I, and comprises peptide-deficient forms of MHC class I molecules in complex with the transporter associated with antigen processing (TAP), the assembly factor tapasin, and the ER chaperones calreticulin and ERp57. The binding of a peptide releases MHC class I from the PLC, and allows for trafficking to the cell surface via the Golgi network (; ). HLA class I alleles have strong influences upon disease progression outcomes in infectious diseases and cancers (; ). Specific alleles are also linked to autoimmune diseases (; ) and drug hypersensitivities. Since the presence of a ‘foreign’ peptide is the key activation signal for CD8 + T cell responses, the peptide-binding characteristics of individual HLA class I molecules are important determinants of their associations with many disease outcomes. This is well-studied in the case of HIV infections. The cell surface stabilities of HLA class I-peptide complexes can be influenced by multiple factors, including the nature of peptide-MHC interactions, the abundance of factors that mediate their assembly, and the extent of peptide-deficient HLA class I expression.
A given HLA class I molecule can bind to a large number of peptides that have specific sequence motifs (for example, ) and length constraints (the HLA class I peptidome, for example those characterized in ). Not all HLA class I binding peptides are transported equivalently by the TAP transporter. The use of peptide libraries fixed at specific positions with single amino acids has revealed strong sequence preferences for peptide transport by TAP. In general, peptide residue 2 (P 2) and the C-terminal residues of peptides (P C) are strong determinants of peptide binding to HLA class I. TAP also has strong preferences within this region; hydrophobic C-terminal residues, generally preferred by HLA class I molecules, are also preferred by TAP. At the P 2 position, however, proline is strongly disfavored by TAP, but highly preferred by a subset of HLA-B molecules - those within the B7 supertype.
The functional consequences of such mismatches in TAP and HLA class I binding preferences are unknown. It can be hypothesized that the mismatch causes suboptimal assembly in the ER, and for some allotypes, reduced cell surface stability and increased ability to sample peptides from unconventional sources. A number of studies have indicated that tapasin, via the PLC, facilitates HLA class I-peptide assembly and also optimizes the HLA class I peptide repertoire towards high affinity sequences (;; ). HLA-B allotypes differ markedly in their dependencies on tapasin for their cell surface expression (; ). Tapasin-independent HLA-B allotypes generally have higher intrinsic stabilities of their peptide-deficient forms , and thus may be more prone to exit the ER as suboptimally loaded versions, particularly when peptide is limiting.
Previous studies have shown that mRNA differences and regulatory polymorphisms affect HLA class I and class II expression (; ). The HLA-B locus is the most polymorphic of the HLA class I loci (and thus the most rapidly evolving), with dominant influences upon disease outcomes. HLA-B alleles do not vary in mRNA expression , but there are known variations in the assembly and peptide-binding characteristics of HLA-B allotypes, as described above. It is unknown whether such variations can result in global cell surface stability differences, ER retention differences and subsequent cell surface expression differences in primary human cells. In this study, we addressed the hypothesis that peptide pool limitations induced by mismatched peptide-binding preferences between TAP and HLA class I allotypes affects cell surface expression levels of HLA class I molecules, via suboptimal assembly.
To address this hypothesis, we used freshly-isolated human lymphocytes and monocytes and quantitative flow cytometry to examine the expression levels of HLA-B alleles in an Ann Arbor, United States cohort of healthy donors. Where expression differences were significant, we also undertook cell surface stability measurements to assess whether these variations explain the expression differences. Finally, we compared exogenous peptide receptivity of HLA-B allotypes with high or low cell surface stability to assess variations. Specificities and relative binding propensities of an anti-HLA-Bw6 monoclonal antibody Allele-dependent differences in stabilities or assembly efficiencies in the ER are expected to culminate in cell-surface expression differences. Based on this expectation, we first assessed whether there are measurable HLA-B cell surface expression differences.
Important points to consider in assessing allelic variations in HLA class I cell surface expression are (a) the specificities of antibodies used for the expression assessments and (b) potential differences in the binding affinities of detecting antibodies towards the HLA class I allotypes that are being compared. We used Luminex bead-based assays to compare the binding of an HLA-B specific antibody to several HLA class I alleles. HLA-B allotypes are categorized as either HLA-Bw4 or HLA-Bw6 serotypes based on their sequences. Differences at positions 77 and 80–83 of the heavy chain determine the presence of a Bw4 or Bw6 epitope. Commercial antibodies are available that target these epitopes, making them the broadest reported panel of HLA-B-specific antibodies. We thus tested the anti-Bw6 and anti-Bw4 monoclonals from One Lambda for their binding specificities to beads carrying individual HLA-A, HLA-B, or HLA-C molecules. Binding of the HLA-conjugated beads to anti-Bw6 as well as W6/32, a pan HLA class I antibody , was first assessed at multiple dilutions (1:10 to 1:220).
Signals obtained for anti-Bw6 binding to beads with individual HLA-A, HLA-B, and HLA-C were normalized relative to those obtained with W6/32, to correct for any difference in HLA class I coupling to beads. The data obtained at 1:50 dilution from two independent measurements are shown in.
The anti-Bw6 antibody was specific for HLA-B alleles with the Bw6 epitope, and showed no binding to any HLA-A or HLA-Bw4 allotypes, although it also recognized some HLA-C alleles. Further analyses of the sequences of the HLA-C alleles that were recognized by anti-Bw6 (residues 77–83) revealed the presence of a sequence motif similar to the Bw6 motif.
These same HLA-C alleles are also recognized by a different commercial anti-Bw6 antibody (Miltenyi). HLA-C alleles that are not recognized by anti-Bw6 have altered sequences in the region corresponding to the Bw6 motif. As discussed below, the majority of heterozygous donors included in the study expressed one HLA-B allele and one HLA-C allele with a Bw6 sequence. Based on mass spectrometric analyses, HLA-C allele expression is shown to be 6 fold lower compared to HLA-B ; thus, within the included donor pool, HLA-B rather than HLA-C is expected to contribute dominantly to the anti-HLA-Bw6 derived signal. A total of 244 healthy donors were recruited and genotyped for the HLA class I locus using next-generation sequencing. Donors who had Bw4/Bw6 heterozygosity at the HLA-B locus or homozygosity for an HLA-Bw6 allele were included for further studies. Within this donor pool, HLA-Bw6 alleles with at least three donors/allele, and a range of peptide-binding preferences (including P 2P; ) were HLA-B.07:02, HLA-B.08:01, HLA-B.15:01, HLA-B.18:01, HLA-B.35:01, and HLA-B.40:01.
Donors with these alleles were selected for Bw6 expression measurements. For the included HLA-Bw6 alleles, the Luminex anti-Bw6/W6/32 ratios were relatively invariant , thus the One Lambda Bw6 antibody could be used for further expression variation assessments. The majority of donors selected for HLA-Bw6 measurements had Bw4/Bw6 heterozygosity at the HLA-B locus, and one HLA-C allele with a Bw6 sequence (HLA-C.01:02, HLA-C.03:02, HLA-C.03:04, HLA-C.07:01, HLA-C.07:02, HLA-C.07:18, HLA-C.12:03, or HLA-C.16:01).
Six donors had HLA-B Bw4/Bw6 heterozygosity, with both HLA-C alleles lacking a Bw6 sequence (HLA-C.04:01, HLA-C.04:04, HLA-C.05:01, HLA-C.06:02 or HLA-C.15:02). Seven donors had HLA-Bw6 and HLA-C homozygosity, and all the HLA-C alleles of these donors had a Bw6 sequence (HLA-C.07:01, HLA-C.07:02, or HLA-C.12:03). For the latter group of donors, the expression measurements shown in and are 50% of the total measured values. As noted above, based on previous mass spectrometric analyses, where HLA-C allele expression is shown to be several-fold lower than HLA-B , HLA-B rather than HLA-C is expected to contribute dominantly to the anti-HLA-Bw6 derived signal in all the donors included in this study. Thus, all donor allele groupings discussed below are based on the relevant HLA-B allele. Expression variations among HLA-Bw6 alleles. Forty-three healthy donors with either heterozygosity for HLA-Bw4/Bw6 or homozygosity for HLA-Bw6 alleles were sorted into six groups based on their Bw6 alleles.
ABC values were calculated by flow cytometry based on staining freshly isolated PBMCs with anti-Bw6 or W6/32 and normalizing the resulting geometric MFI values against beads with known amounts of Fc receptors. Averaged ABC values for each donor are shown, grouped by the donor’s HLA-Bw6 alleles and lymphocyte subset analyzed (B cells (top row), CD4 + T cells (second row), CD8 + T cells (third row), and NK cells (last row)). For homozygous donors, 50% of the derived ABC values are plotted. Bw6 ABC values alone (column 1), W6/32 ABC values alone, (column 2) and the Bw6/W6/32 ABC ratios (column 3) are shown. The number of replicate measurements for each donor and standard errors of the mean are shown in.
Statistically significant differences between alleles were analyzed by one-way ANOVA analysis for each cell type. Each dot represents averaged Bw6, W6/32, or Bw6/W6/32 ABC measurements (n 3) from a single donor. Low cell surface expression levels of HLA-B.35:01 and HLA-B.07:02 in lymphocytes The Bw6 alleles selected for expression measurements included two members of the B7 supertype (B.07:02 and B.35:01), two members of the B44 supertype (B.18:01 and B.40:01), and one member each of the B62 (B.15:01) and B8 (B.08:01) supertypes, representing multiple peptide binding specificities.
Donors were recruited for multiple blood draws across a period of roughly 18 months. Peripheral blood mononuclear cells (PBMCs) were purified and stained with antibodies to identify CD4, CD8, B, and NK cell subsets, and additionally with anti-Bw6 or W6/32. The anti-Bw6 and W6/32 MFI signals from each measurement were calibrated against measurements from beads with known quantities of Fc receptors that were stained with the same concentration of antibodies (anti-Bw6 or W6/32) to determine the respective antibody binding capacities (ABC) on different lymphocyte subsets. Each included donor had at least three ABC measurements performed from independent blood draws, with most donors having greater than three independent measurements. For each donor, averaged Bw6 and W6/32 ABC values are plotted, grouped by the Bw6 allele at the HLA-B locus (, columns 1 and 2). There were differences in HLA-Bw6 ABC values measured between allele groups.
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In general, highest expression is measured for HLA-B.08:01 cells, and lowest expression is measured for HLA-B.07:02 and HLA-B.35:01 in all cell subsets. Based on a one-way ANOVA analysis, the expression differences between HLA-B.08:01 and HLA-B.07:02 are significant in CD4 + and CD8 + T cells, but similar trends are noted in B and NK cell subsets. Differences between HLA-B.08:01 and HLA-B.35:01 are significant in CD4 +, CD8 + T cells and NK cells, but similar trends are noted in B cell subsets. On the other hand, no significant differences between allele groups were measured in any cell type for the W6/32 ABC values (, column 2).
There were, however, donor to donor variations in W6/32 ABC (total HLA class I expression) between donors within the same allele group. To correct for potential overall expression differences that may be related to regulatory polymorphisms, the Bw6/W6/32 ABC ratios were also calculated for each donor and used in a one-way ANOVA analysis for comparisons between alleles (, column 3). The B.08:01 vs B.07:02/B.35:01 differences were maintained or enhanced following the corrections.
The Bw6/W6/32 ABC ratios were significantly higher for HLA-B.08:01 donors compared to B.07:02 donors in all cell types. Additionally, the Bw6/W6/32 ABC ratios were significantly higher for HLA-B.08:01 donors compared to B.35:01 donors in CD4 +, CD8 + T cells and NK cells, and similar trends were noted in B cells. Although other significant differences are noted in the Bw6/W6/32 ratios (for example higher ratios for HLA-B.08:01 compared to HLA-B.15:01 in CD4 and CD8 cells), these differences are not accompanied by corresponding differences in anti-Bw6 ABC values.
Thus, based on the tested Bw6 group of alleles, cell surface expression of HLA-B.07:02 and B.35:01 are low compared to other alleles, and significantly different compared to HLA-B.08:01. The significance of the differences between these alleles is maintained in most cell types after accounting for overall HLA class I expression differences. Although the most significant differences are measured in CD4 + and CD8 + T cells, similar allele-dependent trends are present in all cells.
Notably, both these lowest expressing HLA-B allotypes prefer P 2P peptides that are disfavored for TAP transport. Absence of differences in HLA-B mRNA expression in lymphocytes Allele-dependent variations in RNA levels within cells can explain the surface expression differences , although recent findings indicate that HLA-B transcript levels are relatively invariant across alleles, based on measurments with PBMC. This possibility was further examined using real time polymerase chain reactions (RT PCR). Alleles were selected based on the most significant differences observed in the ABC analysis , and purified CD4 + and CD8 + T cells were used for these analyses. The HLA-B mRNA expression levels for each donor were measured with HLA-B-specific primers (which measure total transcript levels of both HLA-B alleles from each donor).
Pan-HLA class I primers were also used. Shows representative RT PCR experiment for donors expressing indicated HLA-Bw6 alleles (2 -ΔCt values shown are averaged from three technical replicates of the same RNA preparation).
Based on a one-way ANOVA analysis, no significant differences are noted in transcript levels, using either HLA-B or pan HLA class I primers. These findings using cDNA samples from the Ann Arbor healthy donor cohort were consistent with results based on RNA sequencing (RNA-Seq) of samples derived from donors in Africa and Thailand. There were no significant allele-dependent differences between HLA-B mRNA levels in CD4 + T cells, B cells and NK cells, based on samples derived from donors in Africa and Thailand. Some significant associations were observed in the CD8 + T cells, but the significance was lost when donors are stratified by ethnicity to separately represent the majority African donors. Lower global cell surface stabilities of HLA-B.35:01 and HLA-B.07:02 in lymphocytes ER retention differences can also account for cell surface HLA-B expression differences. In a CD4 + T cell line, the rate of assembly and exit from the ER for HLA-B.35:01 is so rapid that binding to peptide loading complex components in the ER is undetectable at the steady state.
Thus, it is unlikely that increased ER retention explains the lower surface expression of HLA-B.35:01. Consistent with this expectation, the intracellular HLA-Bw6 protein levels (quantified as a ratio of the fluorescence signal in fixed relative to fixed and permeabilized cells (fixed/fixed +permeabilized) in flow cytometry experiments are not higher in PBMCs from B.08:01 donors compared to cells from either HLA-B.35:01 or HLA-B.07:02 donors (data not shown). Since differences in cell surface stability (half-life) can be another factor that determines cell surface expression differences, we further quantified and compared global HLA-B cell surface stabilities (half-lives). Freshly isolated PBMCs were treated with brefeldin A (BFA), which blocks forward trafficking of newly synthesized HLA class I to the cell surface. For selected donors within the HLA-Bw6 donor group, MFI values for anti-Bw6 were measured at different time points after BFA treatment to calculate the half-lives in the different lymphocyte subsets. Representative stability plots used for the half-life calculations are shown in, left column. Bw6 half-lives were calculated based on stability plots from individual days, averaged across multiple measurements (made with blood collections on different days from the same donor), and grouped by HLA-Bw6 allele (, right column and ).
HLA-B.08:01, in general, displays high cell surface stability compared to all other HLA-Bw6 allotypes. Based on a one-way ANOVA analysis, the most significant differences are between HLA-B.08:01 and HLA-B.35:01 - allotypes which display the most significant cell surface expression differences.
The differences are most significant in CD8 + T cells, although significant trends are also noted in CD4 + T cells and NK cells. In pairwise comparisons based on a Welch’s t-test (not shown), the half-life differences between HLA-B.08:01 and HLA-B.35:01 are significant in all cells, and those between HLA-B.08:01 and HLA-B.07:02 are significant in all cells except B cells. Overall, the half-life measurements indicate that the high steady state cell-surface expression levels of HLA-B.08:01 relative to HLA-B.08:01 and HLA-B.07:02 in lymphocytes can be explained by the higher cell surface stability of HLA-B.08:01. Cell surface stabilities of HLA-Bw6 allotypes are allele-dependent. Left column: Representative cell surface stability measurements of Bw6 epitopes on freshly isolated lymphocytes derived from Bw4/Bw6 heterozygous donors expressing HLA-B.08:01, HLA-B.35:01 or HLA-B.07:02 as the Bw6 allotype. Right column: Bw6 half-lives from are grouped by Bw6 allele. Each data point represents data derived from an individual donor, with the open data points representing donors shown in the left panel.
Mean half-life values are shown for each donor, measured using freshly isolated cells from at least two independent blood collections for each donor. The number of replicate measurements for each donor and standard errors of the mean are shown in. Statistical significance is based on one-way ANOVA analysis. Altered HLA-B expression and stability patterns in monocytes compared to lymphocytes Thus far, expression and stability experiments ( and ) were performed on lymphocyte subsets, since they are the most abundant cells in PBMC, and because lymphocytes share a common lineage, and are thus most comparable to each other. We next assessed whether the differences measured in lymphocytes are maintained in additional antigen presenting cell subsets (APC). We recruited back a subset of donors for expression assessments in monocytes, which are more abundant in blood than dendritic cells (DC), making the measurements feasible using fresh undifferentiated PBMCs.
A subset of donors from the B.08:01, B.07:02 and B.35:01 allele groups (alleles with the most significant lymphocyte HLA-B expression and stability differences) were recruited back for blood draws over an additional period of roughly 2 months. PBMCs were purified and stained with antibodies to identify lymphocyte and monocyte subsets, and additionally with anti-Bw6 or W6/32, and analyzed by flow cytometry, as for. For each donor, averaged Bw6 and W6/32 ABC values in CD4 + and CD8 + T cells and monocytes are plotted, grouped by the Bw6 allele. Expression differences between B.08:01 and B.07:02/B.35:01 were significant in CD4 + and CD8 + T cells , consistent with the previous measurements with the larger pool of donors. Surprisingly, however, for the parallel monocyte measurements within the same pool of donors, the expression differences were reversed, with B.08:01 displaying lower expression than both B.35:01 and B.07:02, and the differences reaching statistical significance for B.35:01. No statistically significant differences were measured for the W6/32 ABC values , although the overall patterns of expression resembled those obtained with Bw6.
When the monocyte ABC values for each donor were normalized relative to their CD4 + and CD8 + T cell ABC values and donors grouped by their Bw6 alleles, monocytes displayed a significant induction of expression relative to CD4 + and CD8 + T cells for B.35:01 and B.07:02, but not for B.08:01. Corresponding half-life measurements indicated a significant reduction in B.08:01 half-life in monocytes compared with CD4 + and CD8 + T cells, whereas the differences between monocytes and lymphocytes were not significant for B.07:02 and B.35:01.
Indeed, in monocytes, no significant half-life differences were measured between B.08:01 and B.35:01/B.07:02. Together, these findings indicated both allele and cell type dependent variations in HLA-B cell surface expression and stability patterns. Altered patterns of HLA-Bw6 surface expression and stability in monocytes compared with lymphocytes. A and B: Blood donations were again obtained from a subset of donors represented in the measurements. Averaged ABC values measured with anti-Bw6 ( A) or W6/32 ( B) for each donor are shown, grouped by the donor’s HLA-Bw6 alleles and cell subsets. C: For each donor represented in A and B, Bw6 ABC values in lymphocytes are normalized relative to the monocyte values from the same donor, and grouped by the donor’s HLA-Bw6 alleles and cell subsets. Averaged ABC values and data replicates obtained for plots in A-C are shown in.
D: Cell surface stability measurements (obtained as described in ) of CD4 + and CD8 + T cells in comparison to monocytes. E: Cell surface stability measurements in monocytes of indicated HLA-Bw6 allotype.
Half-life values and data replicates obtained for the plots in D and E are shown as. A-E: Each point represents data from a single donor. Statistical significance is based on one-way ANOVA analysis.