The Impact of Live Audience Participation Teaching on Medical Education at The Surgical Scousers, an Undergraduate Surgical Society

This article was migrated. The article was not marked as recommended. Background: The use of Live Audience Participation (LAP) allows students to respond to questions anonymously and receive instant feedback. Electronic devices promote interaction and participation from learners which has the potential to further engage students and lead to an increased level of learning. It is important however to evaluate the affordances and limitations of such devices. Objectives: The aim of our study was to assess the aptness, utility, practicalities and acceptability of LAP during lectures. Methods: The interactive 'PollEverywhere™' tool was used during 5 extra-curricular lectures, organized by 'The Surgical Scousers' society, allowing student participation to anonymously answer questions. Live results were displayed instantly and data was collected prospectively in 2013. Results: Out of 523 responses, 417 were correct. Students were also able to ask questions and give live feedback. Students gave positive feedback highlighting how LAP maintained their attention. The majority of students expressed that they would not have asked the same questions in a conventional set up. Conclusion: We have demonstrated that the use of LAP holds the attention of students, provides opportunity to ask questions, and facilitates ironing out any misconceptions within subject areas. However, interactive devices have certain inherent limitations, namely cost and potential to go wrong. The majority of literature focuses on students' views towards interactive devices therefore. Further studies are required to assess the impact of interactive devices on learning outcomes in medical education.

Proliferatory defect of invariant population and accumulation of non-invariant CD1d-restricted natural killer T cells in the joints of RA patients

OBJECTIVES

While numerical and functional defects of invariant NKT cells have been demonstrated in rheumatoid arthritis (RA), the detailed characterization of proliferative and secretory responses following CD1d-mediated presentation is lacking; the presence of non-invariant populations has never been assessed in human autoimmunity. We have evaluated both invariant and non-invariant populations in the blood and synovial fluid from patients to assess feasibility of NKT cell-directed manipulations in RA.

METHODS

NKT cell populations were quantified by anti-CD4/anti-Vα24 staining and/or CD1d tetramers. Proliferation was measured in cultures of mononuclear cells following stimulations with αGalCer and cytokine secretion determined by multi-bead assay.

RESULTS

We have confirmed a proliferative defect of iNKT cells in both peripheral blood and synovial fluid from RA patients, but no changes in baseline frequencies. Moreover, we have detected an enlargement of non-invariant cell pool in synovial fluid samples. In addition, we noted an evident Th2 shift following exposure to αGalCer and pronounced IL-6 secretion.

CONCLUSIONS

While RA patients suffer from defective proliferative responses of invariant NKT cells, non-invariant cells accumulate at the site of inflammation. While stimulation with αGalCer results in reduced TNF-α and increased suppressive IL-10, abundantly produced IL-6 could potentially contribute to the induction of Th17 cells in the joints.

At the crossroads: mucosal immunology of the larynx

The larynx sits at the crossroads between gastrointestinal and respiratory tracts. Besides its intrinsic importance in breathing, swallowing and voice production, the larynx is also exposed to unique immunological challenges. Given the propensity of chronic inflammatory conditions such as chronic laryngitis, which affects up to 20% of Western populations, it is surprising that our understanding of the immunology of this organ remains relatively limited. Recent work on the immunological architecture of the laryngeal mucosa, and its changes that result from external challenges and inflammatory conditions, provided valuable insight into the fascinating immunology of this organ. The lessons learnt from these investigations may go beyond devising improved therapy for chronic laryngeal inflammation. Establishing whether and how the laryngeal mucosa may be involved in the modulation of wider mucosal responses may provide novel routes to the treatment of inflammatory diseases of the respiratory and alimentary tracts such as asthma and inflammatory bowel disease.

Immunologic Response of the Laryngeal Mucosa to Extraesophageal Reflux

Objectives:

Extraesophageal reflux is common. The treatment costs are high, and there are associations with other diseases, including laryngeal cancer. Our studies of the mucosal immune response to this common inflammatory disease suggest an important role for the nonclassic antigen-presenting molecule CD1d in the response to inflammation. This study was performed to further explore the relationship between the CD1d–NKT cell–iGb3 axis and reflux.

Methods:

We carried out a prospective study of laryngeal biopsies from 12 patients with laryngopharyngeal reflux and 11 controls. Quantitative multiple-color immunofluorescence using antibodies for lymphocytes (CD3, CD161) and classic and nonclassic major histocompatibility complex (I, II, β2m, CD1d) was performed, and univariate and multivariate analysis and co-localization measurements were applied.

Results:

Epithelial major histocompatibility complex class I and II expression was unchanged by reflux, but expression of CD1d increased (p < 0.05; luminal layers) and confidence intervals diminished in the reflux group. Co-localization of NKT cells with CD1d increased in patients (p < 0.01); iGb3 exhibited strong expression throughout all layers of the laryngeal epithelium.

Conclusions:

These data indicate a role for the CD1d–NKT cell–iGb3 axis in response to extraesophageal reflux in humans. This represents a useful target for novel diagnostics and treatments for this common condition.

The mucosal immune response to laryngopharyngeal reflux

RATIONALE

Laryngopharyngeal reflux (LPR) affects up to 20% of Western populations. Although individual morbidity is usually moderate, treatment costs are high and there are associations with other diseases, including laryngeal cancer. To date, there have been no studies of the mucosal immune response to this common inflammatory disease.

OBJECTIVES

To determine the mucosal immune response to LPR.

METHODS

We performed a prospective immunologic study of laryngeal biopsies from patients with LPR and control subjects (n = 12 and 11, respectively), and of primary laryngeal epithelial cells in vitro.

MEASUREMENTS AND MAIN RESULTS

Quantitative multiple-color immunofluorescence, using antibodies for lymphocytes (CD4, CD8, CD3, CD79, CD161), granulocytes (CD68, EMBP), monocytic cells (CD68, major histocompatibility complex [MHC] class II), and classical and nonclassical MHC (I, II, beta(2)-microglobulin, CD1d). Univariate and multivariate analysis and colocalization measurements were applied. There was an increase in percentage area of mucosal CD8(+) cells in the epithelium (P < 0.005), whereas other leukocyte and granulocyte antigens were unchanged. Although epithelial MHC class I and II expression was unchanged by reflux, expression of the nonclassical MHC molecule CD1d increased (P < 0.05, luminal layers). In vitro, laryngeal epithelial cells constitutively expressed CD1d. CD1d and MHC I expression were inversely related in all subjects, in a pattern which appears to be unique to the upper airway. Colocalization of natural killer T (NKT) cells with CD1d increased in patients (P < 0.01).

CONCLUSIONS

These data indicate a role for the CD1d-NKT cell axis in response to LPR in humans. This represents a useful target for novel diagnostics and treatments in this common condition.

Altered gastric corpus expression of tissue inhibitors of metalloproteinases in human and murine Helicobacter infection

BACKGROUND

Matrix metalloproteinases (MMPs) have roles in inflammation and other processes relevant to the architectural disturbances seen in the gastric mucosa in response to Helicobacter pylori infection. Upregulation of MMPs has been reported in H pylori infection, but there are no detailed reports regarding altered production of their inhibitors, the tissue inhibitors of metalloproteinases (TIMPs).

AIMS

To investigate changes in the abundance of TIMPs in human gastric corpus mucosa and murine stomach in Helicobacter infection, and to study cellular sources in man.

METHODS

Gastric corpus biopsy samples were assessed for abundance of mRNA or protein for TIMP-1 to -4 by real-time quantitative PCR or western blotting, respectively. Antral and corpus biopsies were processed for histology, H pylori status and inflammatory scoring. Cellular sources of TIMP-1, -3 and -4 were examined by indirect immunohistochemistry. Circulating gastrin was measured by radioimmunoassay. Also, abundance of TIMP-1, -3 and -4 mRNA in the stomach of Helicobacter felis infected mice post-infection was compared with that of uninfected control animals.

RESULTS

Compared with uninfected patients, mRNA and protein for TIMP-1, -3 and -4 were significantly more abundant in the gastric corpus of H pylori infected subjects. Gastric TIMP expression did not differ significantly between hyper- and normogastrinaemic subjects within the H pylori negative and positive groups. There was no difference in mRNA abundance for MMP-3 or -8. Immunohistochemistry showed TIMP proteins localised to gastric epithelial, stromal cells and inflammatory cells. Murine H felis infection was associated with upregulation of TIMP-1 and -3 mRNA.

CONCLUSIONS

Helicobacter infection is associated with upregulation of specific TIMPs (TIMP-1 and -3) in glandular epithelium and stroma. It is suggested that increased expression of specific protease inhibitors in the corpus mucosa may exert important effects on extracellular matrix remodelling and influence the outcome of H pylori infection.

Optimal method for isolation of human peritoneal mesothelial cells from clinical samples of omentum

INTRODUCTION

Human peritoneal mesothelial cells (HPMC) are a valuable research tool for understanding the molecular biology of several pathologies, in both monolayer and three dimensional models. We compared different methods of HPMC isolation and assessed their outcome as well as fibroblast contamination, a common problem encountered during isolation.

METHODS

1-3cm(3) samples of omentum were collected from 40 consenting patients undergoing elective gastrointestinal surgery. A total of 11 samples were incubated in 0.05% trypsin solution for 20 minutes at 37 degrees C (group A) and 29 in 0.25% trypsin (15 samples for 10 minutes (group B) and 14 for 20 minutes (group C)). Following digestion cells were re-suspended and cultured in supplemented Ham's F-12 medium containing 10% foetal calf serum (FCS), penicillin-streptomycin, glutamine, insulin, transferrin and hydrocortisone. Positive outcomes were absence of fibroblast contamination and satisfactory HPMC growth to confluence in a characteristic cobblestone pattern. Cytokeratins 5, 8, 18, Vimentin, Ber-Ep4 and Factor VIII were used to characterise HPMC and fibroblasts by immunohistochemistry.

RESULTS

None of the 11 samples in group A yielded HPMC. 14 of 29 samples digested with 0.25% trypsin yielded HPMC: 10 of 14 yielded HPMC in group C versus four of 15 samples in group B (p = 0.02). Fibroblast contamination occurred in eight samples in group B versus three in group C.

CONCLUSION

Optimal results are achieved with a 20 minute digestion in 0.25% trypsin. Fibroblast contamination could not be avoided completely. Other factors may minimise fibroblast contamination such as minimal tissue manipulation and early collection during surgery.

Inflammatory gene expression patterns revealed by DNA microarray analysis in TNF-alpha-treated SGBS human adipocytes

We report here the use of human inflammation arrays to study the inflammatory gene expression profile of TNF-alpha- treated human SGBS adipocytes. Human preadipocytes (SGBS) were induced to differentiate in primary culture, and adipocyte differentiation was confirmed, using Oil Red O staining. We treated the differentiated adipocytes with TNF-alpha, and RNA from differentiated adipocytes with or without TNF-alpha treatment was hybridized to MWG human inflammation arrays to compare expression profiles. Eleven genes were up- or down-regulated in TNF-alpha-treated adipocytes. As revealed by array analysis, among 6 up-regulated genes, only eotaxin-1, monocyte chemoattractant protein-1 (MCP-1), and vascular cell adhesion molecule 1 isoform a precursor (VCAM1) were confirmed by real-time polymerase chain reaction (PCR). Similarly, among 5 down-regulated genes, only IL-1 family member 5 (IL1F5), a disintegrin and metalloprotease with thrombospondin motifs-1 preproprotein (ADAMTS1), fibronectin 1 isoform 1 preprotein (FN1), and matrix metalloproteinase 15 preprotein (MMP15) were confirmed by real-time PCR. There was a substantial increase (50-fold) in eotaxin-1 in response to TNF-alpha. Taken together, we have identified several inflammatory molecules expressed in SGBS adipocytes and discovered molecular factors explaining the relationship between obesity and atherosclerosis, focusing on inflammatory cytokines expressed in the TNF-alpha-treated SGBS cells. Further investigation into the role of these up- or down-regulated cytokine genes during the pathological processes leading to the development of atherosclerosis is warranted.

Do NK cells regulate human autoimmunity?

Natural killer cells have been shown to regulate autoimmune responses under experimental conditions in animals. However, a similar role for human NK cells has not been investigated, although NK cells constitute a significant fraction of the infiltrating cells in a range of autoimmune diseases. This review investigates the evidence, both theoretical and experimental, for the involvement of these cells in human immunopathology.

Natural killer cells in the synovial fluid of rheumatoid arthritis patients exhibit a CD56bright,CD94bright,CD158negative phenotype

BACKGROUND

Natural killer (NK) cells play an important role in several animal models of autoimmunity by modulating T-cell responses, but it is unclear whether human NK cells have similar functions.

METHODS

We characterized the phenotype of NK cells in synovial fluid (SF) and peripheral blood (PB) of patients with rheumatoid arthritis (RA) and in healthy control subjects using flow cytometry and quantitative PCR.

RESULTS

The proportions of NK cells in PB and SF of RA patients were not significantly different from those in healthy PB. However, the SF NK cell phenotype was strikingly different, with increased CD94 and CD56 densities and greatly reduced proportions of cells expressing CD158a/b. These cells also had reduced mRNAs coding for CD158a/b and low perforin levels compared with RA PB and healthy PB NK cells.

CONCLUSIONS

We identified a novel phenotype of SF NK cells that is of potential significance in RA. Experiments are now under way to determine the function of these SF NK cells and their potential role in RA.

HLA-G inhibits rolling adhesion of activated human NK cells on porcine endothelial cells

Human NK cells adhere to and lyse porcine endothelial cells (pEC) and therefore may contribute to the cell-mediated rejection of vascularized pig-to-human xenografts. Since MHC class I molecules inhibit the cytotoxic activity of NK cells, the expression of HLA genes in pEC has been proposed as a potential solution to overcome NK cell-mediated xenogeneic cytotoxicity. HLA-G, a minimally polymorphic HLA class I molecule that can inhibit a wide range of NK cells, is an especially attractive candidate for this purpose. In this study we tested whether the expression of HLA-G on pEC inhibits the molecular mechanisms that lead to adhesion of human NK cells to pEC and subsequent xenogeneic NK cytotoxicity. To this end two immortalized pEC lines (2A2 and PED) were stably transfected with HLA-G1. Rolling adhesion of activated human NK cells to pEC monolayers and xenogeneic cytotoxicity against pEC mediated by polyclonal human NK lines as well as NK clones were inhibited by the expression of HLA-G. The adhesion was partially reversed by masking HLA-G on pEC with anti-HLA mAbs or by masking the HLA-G-specific inhibitory receptor ILT-2 on NK cells with the mAb HP-F1. The inhibition of NK cytotoxicity by HLA-G was only partially mediated by ILT-2, indicating a role for other unknown NK receptors. In conclusion, transgenic expression of HLA-G may be useful to prevent human NK cell responses to porcine xenografts, but is probably not sufficient on its own. Moreover, the blocking of rolling adhesion by HLA-G provides evidence for a novel biological function of HLA molecules.

Multiple receptors for HLA-G on human natural killer cells

HLA-G is the putative natural killer (NK) cell inhibitory ligand expressed on the extravillous cytotrophoblast of the human placenta. Killing of the class I negative human B cell line 721.221 by NK cells is inhibited by the expression of HLA-G. This inhibition is dependent on a high level of HLA-G expression. In the present study, the nature of the receptors that mediate the inhibition has been studied with 140 NK cell lines from two donors and 246 NK clones from 5 donors by blocking the inhibition using monoclonal antibodies against the known NK inhibitory receptors: CD158a, CD158b, and CD94. Both CD94 and the two CD158 proteins can function as receptors, although the former clearly predominates. In many cases, a combination of antibodies to these receptors is required to achieve maximal reversal of inhibition. Moreover, in at least one-third of the NK cells that are inhibited by HLA-G, these antibodies alone or in combination do not reverse inhibition, strongly suggesting the existence of a third major unidentified receptor for HLA-G.

Impaired spontaneous endocytosis of HLA-G

HLA-G is a class Ib (non-classical) major histocompatibility complex (MHC) protein expressed at the maternal-fetal interface that inhibits natural killer (NK) cell-mediated lysis in an allotype-independent manner. Here we report that the spontaneous endocytosis of HLA-G is severely reduced because of its short cytoplasmic tail. Class I (classical) MHC proteins on the surface of B cell transfectants detected by primary and secondary antibodies underwent endocytosis at a moderate rate, whereas HLA-G, chimeric proteins consisting of the extracellular domains of HLA-C with the C-terminal sequence of HLA-G, or glycophosphatidylinositol-tailed HLA-C proteins, were not efficiently internalized. In addition, a mutant of beta 2-microglobulin (Ser88Cys) that could be specifically labeled with Texas red (or other fluorescent probes) and exchanged into class I or class Ib MHC proteins was employed to study spontaneous internalization of MHC proteins by a non-perturbative method independent of an antibody ligand. These data are discussed in terms of both the role of HLA-G expressed on the fetal trophoblast and the function of the cytoplasmic tail in class I MHC proteins.

The class I MHC homologue of human cytomegalovirus inhibits attack by natural killer cells

Recognition and destruction of virus-infected cells by class I major histocompatibility complex (MHC) restricted cytotoxic T lymphocytes (CTL) is a central part of the immune system's attempts to control and eliminate virus infection. It is therefore not surprising that many viruses have evolved strategies to interfere with the processing and presentation of peptide antigen on class I MHC molecules (reviewed in ref. 1). These mechanisms act to prevent or reduce expression of MHC molecules at the cell surface. However, many natural killer (NK) cells are able to recognize and destroy host cells that no longer express class I MHC molecules (the 'missing self' hypothesis). Thus, any virus-infected cell that has lost cell-surface expression of MHC class I to avoid CTL attack should become susceptible to NK-cell-mediated destruction. We describe here the first example, to our knowledge, of a viral strategy to evade immune surveillance by NK cells.

The binding site of NK receptors on HLA-C molecules

The protection of cells expressing class I HLA molecules from NK lysis is mediated by natural killer cell inhibitory receptors (NKIR). Using site-directed mutagenesis, residues on HLA-C that determine the locus specificity (alphaVal-76), allotype group specificity (a dimorphism alphaAsn-80/Lys-80), and affinity of NKIR binding (a second pair of dimorphisms, alphaAla-73, Asp-90 or alphaThr-73, Ala-90) have been identified. Thus the "footprint" of the NKIR on the alpha1 helix of the class I MHC molecule HLA-C and its associated beta strands are similar in position to the site occupied by superantigens on and behind the alpha1 helix of the class II MHC molecule HLA-DR1, but further toward its C-terminus. The intermediate affinity binding of NKIR to HLA-C, determined by alpha73 and alpha90, has an essential role in preventing cross-reactivity and ensuring the availability of NK cells for immunosurveillance; low affinity and high affinity mutants are both physiologically impaired.

Human NK cells: their ligands, receptors and functions

The expression, or lack thereof, of class I MHC glycoproteins has a marked influence on natural killer cell function. Cells which do not express class I MHC molecules are susceptible to lysis by NK cells, and transfection of these targets with class I MHC genes can render these cells resistant to NK attack. This inhibition of NK-killing is mediated by a novel family of receptors expressed mainly on NK cells, but also found on some T-cells. The function of these class I MHC binding receptors when expressed on T-cells is discussed also and a novel co-stimulatory activity of NKAR described. Lastly, a novel mechanism by which human cytomegalovirus evades immune surveillance by NK cells is documented.

Enhancement of class II-restricted T cell responses by costimulatory NK receptors for class I MHC proteins

An important feature of the human immune system is the ability of T cells to respond to small quantities of antigen. Class II major histocompatibility complex (MHC)-restricted T cells that expressed a costimulatory natural killer (NK) cell receptor for class I MHC proteins were cloned. In the presence of low doses of superantigen, the proliferative response of these T cell clones was three- to ninefold greater when the T cells were costimulated by way of the NK receptor. Thus, the action of costimulatory NK receptors on T cells may play a significant role in initiating and sustaining immune responses.

Protection from natural killer cell-mediated lysis by HLA-G expression on target cells

The outermost layer of the human placenta is devoid of classical class I human leukocyte antigens (HLA-A, HLA-B, and HLA-C) and class II proteins (HLA-DR, HLA-DQ, and HLA-DP). Although this prevents recognition by maternal T lymphocytes, the lack of class I molecules leaves these cells susceptible to attack by natural killer (NK) cells. However, trophoblast cells directly in contact with the maternal tissues express the class I molecule HLA-G, which may be involved in protecting the trophoblast from recognition by NK cells. Here evidence is provided that expression of HLA-G is sufficient to protect otherwise susceptible target cells from lysis by activated NK1 and NK2 cell lines and clones that are specific for distinct groups of HLA-C alleles. The receptors on NK cells that recognize HLA-G are also identified.

Protection from lysis by natural killer cells of group 1 and 2 specificity is mediated by residue 80 in human histocompatibility leukocyte antigen C alleles and also occurs with empty major histocompatibility complex molecules

Recognition of major histocompatibility complex class I molecules by natural killer (NR) cells leads to inhibition of target cell lysis. Based on the capacity of different human histocompatibility leukocyte antigen (HLA)-C and HLA-B molecules to inhibit target cell lysis by NK lines and clones, three NK allospecificities have been defined: NK1 and NK2 cells are inhibited by different HLA-C allotypes and NK3 cells by some HLA-B allotypes. The NK1 and NK2 inhibitory ligands on target cells correspond to a dimorphism of HLA-C at residues 77 and 80 in the alpha 1 helix: Asn77-Lys80 in NK1 and Ser77-Asn80 in NK2 inhibitory ligands. It has been reported that protection from NK1 killers depended on the presence of the Lys residue at position 80, an upward pointing residue near the end of the alpha 1 helix (and not on Asn77), whereas inhibition of NK2 effector cells required Ser77, a residue deep in the F pocket and interacting with the peptide (and not Asn80). As part of ongoing experiments to investigate the structural requirements for NK cell inhibition by HLA-C locus alleles, we also examined the effects of mutations at residues 77 and 80 on the ability of HLA-C alleles to confer protection from NK lysis. We present data confirming that the NK1 specificity depended on Lys80 (and not on Asn77); however recognition of NK2 ligands by NK cells was also controlled by the amino acid at position 80 (Asn), and mutation of Ser77 had no effect. Furthermore, bound peptide was shown to be unnecessary for the inhibition of NK cell-mediated lysis since HLA-C molecules assembled in the absence of peptide in RMA-S cells at 26 degrees C were fully competent to inhibit NK cells specifically. The implications of these data for peptide-independent recognition of HLA-C by NK receptors are discussed.

Differences in peptide-binding specificity of two ankylosing spondylitis-associated HLA-B27 subtypes

Two HLA-B27 subtypes, B*2702 and B*2705, both associated with ankylosing spondylitis, were tested for binding affinity with a panel of polyalanine model nonapeptides carrying Arg at position 2 (P2) and a series of different amino acids at position 9 (P9). The alpha chains were isolated from BTB(B*2705), C1R/B*2702 (a B*2702 transfectant cell line) and from the NW (B*2702) cell line that has a peculiar peptide presentation behavior. Peptide binding was measured by the HLA alpha chain refolding assay. The results obtained show that: 1) Peptides with basic residues (Arg and Lys) and also aliphatic (Leu) and aromatic (Phe and Tyr) peptides at P9 have a similar high affinity in the binding to B*2705; 2) B*2702 binds well to P9 aliphatic and aromatic peptides but only very weakly to P9 basic peptides. Since both B*2702 and B*2705 are associated with AS the presumed arthritogenic peptide is hypothesized to have an aromatic or aliphatic residue at position 9. Peptides with basic residues in this position would be excluded as candidates because of their low binding affinity with B*2702.

A critical role for conserved residues in the cleft of HLA-A2 in presentation of a nonapeptide to T cells

The peptide binding cleft of the class I human histocompatibility antigen, HLA-A2, contains conserved amino acid residues clustered in the two ends of the cleft in pockets A and F as well as polymorphic residues. The function of two conserved tyrosines in the A pocket was investigated by mutating them to phenylalanines and of a conserved tyrosine and threonine in the F pocket by mutating them to phenylalanine and valine, respectively. Presentation of influenza virus peptides and of intact virus to cytolytic T lymphocytes (CTLs) was then examined. The magnitude of the reduction seen by the mutation of the two tyrosines in the A pocket suggests that hydrogen bonds involving them have a critical function in the binding of the NH2-terminal NH3+ of the peptide nonamer and possibly of all bound peptide nonamers. In contrast, the mutations in the F pocket had no effect on CTL recognition.

A cross-species functional interaction between the murine major histocompatibility complex class I alpha 3 domain and human CD8 revealed by peptide-specific cytotoxic T lymphocytes

The monomorphic cell surface glycoprotein CD8 acts as co-receptor in the recognition of peptide-major histocompatibility complex (MHC) class I complexes by cytotoxic lymphocytes (CTL) by binding to the monomorphic alpha 3 domain of the class I molecule. Positions 227 and 245 in the class I alpha 3 domain appear to be especially important for this interaction. Recent reports suggest there is no interspecies recognition between CD8 and MHC class I. In this study, hybrid genes from human class I HLA-A0201 and murine class I H-2Kb were transfected into human and mouse cells and tested in Cr-release assays using HLA-A0201-restricted influenza A matrix peptide-specific CTL as effectors. Transfected cells expressing chimeric genes comprising the alpha 1 and alpha 2 domains from HLA-A0201 together with the H-2Kb alpha 3 domain were lysed as effectively as wild-type HLA-A0201 and in both cases, killing was blocked by anti-CD8 antibody equally well. These results indicate that human CD8 can interact with the alpha 3 domain of murine class I to the same level as human class I.

Genetic modulation of antigen presentation by HLA-B27 molecules

In studies of antigenic peptide presentation, we have found a healthy volunteer whose lymphoblastoid cells were unable to present three different virus-derived epitopes to cytotoxic T lymphocytes (CTL) despite expressing the correct restricting HLA-B27 molecules on the cell surface. B cell lines were established from other members of the donor's family, including individuals suffering from ankylosing spondylitis and related diseases, and were tested for their ability to function as target cells in the same assay. None of the eight B cell lines that expressed HLA-B27 presented a known peptide epitope to CTL. However, cells from a family member that expressed HLA-B8 could present an epitope peptide restricted by that molecule. The B27 molecule in this family proved to be the B2702 subtype on isoelectric focusing gels, appearing in exactly the same position as B2702 from other cell lines that did present the peptide. To exclude mutations resulting in noncharged amino acid substitutions, cDNA coding for B2702 was cloned from the proband's cell line and sequenced. No coding changes were found. The cloned cDNA was transfected into HLA-A- and B-negative HMy/C1R cells, and the B2702 molecules generated in this environment rendered these cells, after incubation with peptide, susceptible to lysis by peptide-specific CTL. These data are compatible with the presence of a factor(s), possibly HLA linked, interfering with antigen presentation by otherwise normal B2702 molecules in this family.

A cluster of mutations in HLA-A2 alpha 2 helix abolishes peptide recognition by T cells

In order to investigate the regions of HLA-A2 that control peptide-specific cytotoxic T lymphocyte (CTL) recognition, 37 HLA-A2 genes coding for 50 point mutations that span the alpha 2 helix were synthesized by the technique of saturation mutagenesis. Twenty-nine of these genes, which code for 41 point mutations, were transfected into C1R cells and used as targets in cytotoxicity assays, in the presence of influenza-A matrix peptide 58-68 with specific CTL as effectors. All the transfectants were recognized fully by matrix peptide-specific CTL apart from those with amino acid substitutions at positions 152, 154, 155, 156, or 161, which led to a total loss of recognition and those with mutations at residue 27 or a double mutation at 138 and 150, which were recognized in an intermediate manner. The clustering of the crucial residues that emerges may reflect direct interaction of their side-chains with peptide or the CTL receptor.

Sequence analysis of HLA-Bw53, a common West African allele, suggests an origin by gene conversion of HLA-B35

In the West African population of the Gambia the class I antigen HLA-Bw53 is found at high frequency. We used the polymerase chain reaction to amplify cDNA from an individual homozygous for this allele and determined the nucleotide sequence of the polymorphic alpha 1 and alpha 2 domains. The HLA-Bw53 sequence is identical to HLA-B35 except for a short sequence at the 3' end of exon 2 (encoding the alpha 1 domain) which specifies a Bw4 rather than a Bw6 motif. This suggests an origin for HLA-Bw53 involving a gene conversion of HLA-B35 by an allele containing this Bw4 sequence. The alpha 2 domain shared by HLA-Bw53, -B35, and -Bw58 is particularly common in sub-Saharan Africans.