Biologic and chemical characterization of HLA antigens in human serum.

HLA antigens of both the A and B loci were shown to be associated with the high density lipoprotein fraction of serum prepared by ultracentrifugal flotation. HLA-A9 antigens were purified 100-fold with essentially complete recovery by a simple procedure of high density lipoprotein preparation involving precipitation with polyanions and ultracentrifugal flotation. The purified lipid-associated antigen was immunogenic since it elicited the formation of cytotoxic xenoantibodies in rabbits. Serum HLA-A9 antigens were found by immunoprecipitation and gel electrophoresis to consist of a 45,000 m.w. heavy chain associated with beta2-microglobulin. The size of the HLA-lipid complex (less than 190,000 m.w.) and of the HLA-deoxycholate complex (less than 102,000 m.w.) suggests that HLA antigens are shed into plasma as a complex of a single HLA molecule and a single beta2-microglobulin chain, associated with boundary lipid.     

The monoclonal antibody CR11-351 discriminates HLA-A2 variants identified by T cells

Serologic and immunochemical assays have shown that the monoclonal antibody (MoAb) CR11-351 recognizes a determinant expressed by HLA-A2 and A28 alloantigens. The MoAb CR11-351 blocks the cytotoxicity of some, but not all, anti-HLA-A2 and anti-HLA-A28 alloantisera tested. These findings suggest that each allospecificity consists of several determinants, only some of which are spatially close to the determinant defined by the MoAb CR11-351. The binding of the MoAb CR11-351 to HLA-A2 lymphoid cells is not effected by their precoating with the HLA-A, B-specific MoAb CR10-214, Q6/64, and 6/31 but is enhanced by at least 20% by the MoAb CR10-131, CR10-402 and by the beta 2-m-specific MoAb NAMB-1. The MoAb CR11-351 did not react with one of four HLA-A2 variants which are indistinguishable with conventional anti-HLA-A2 sera, but are not recognized by "normal" HLA-A2-restricted cytotoxic T cells and possess structurally distinct HLA-A2 heavy chains. Therefore the MoAb CR11-351 provides the first evidence of a serologically detectable difference between the four HLA-A2 variants and "normal" HLA-A2 antigens.     

A study of functionally active amino acids involved in the interaction of HLA-A2 or HLA-A3 molecules with cytolytic T lymphocytes

A large series of HLA-A2/HLA-A3 recombinant genes were generated by using the in vivo recombination technique. These genes have each been modified in the last two-thirds of the third exon such that one or several HLA-A2-specific substitutions have been made in the HLA-A3 gene and vice versa. The recombinant genes were transfected into the murine cell line P815 and the transfectants were used as targets for a series of 20 human CTL lines or clones specific for HLA-A2 or HLA-A3, or restricted by HLA-A2 and specific for influenza A. Several patterns of anti-HLA-A2, anti-HLA-A3, and HLA-A2-restricted anti-influenza CTL activity were observed and when uncloned cell lines were studied, a progressive selection of some clones with a similar pattern of activity was regularly found. From the comparison of these different patterns the following conclusions can be drawn: 1) In most but not all cases both domains of the class I molecule were essential for CTL recognition, but residue 152 was critically important for the majority of CTL tested; 2) amino acids 114/116 were also critical in most cases, and their position close to amino acid 152 in the tertiary structure of the molecule may have some functional significance; and 3) amino acid 161, although highly conserved, plays an unexpected but very important role in CTL function.     

Clonal T lymphocyte recognition of the fine structure of the HLA-A2 molecule

A human alloimmune cytotoxic T lymphocyte (CTL) clone (4E4) was generated against the HLA-A2 molecule. Lysis of 51Cr-labeled HLA-A2 target cells was blocked by monoclonal antibodies (mAb), including mAb PA2.1 (anti-HLA-A2), mAb BB7.2 (anti-HLA-A2), mAb 4B (anti-HLA-A2-plus-A28), mAb MA2.1 (anti-HLA-A2-plus-B17), and mAb W6/32 (anti-HLA-A,B,C), which are directed against different serologic epitopes on the HLA-A2 molecule. However, HLA-A2 mutant lines lacking the serologic epitope recognized by mAb BB7.2 (anti-HLA-A2) were efficiently lysed by CTL 4E4. Thus, although mAb may block cytolysis, the HLA-A2 epitope recognized the 4E4 CTL clone is distinct from the HLA-A2-specific epitope recognized by serologic reagents. Moreover, analysis of HLA-A2 population variants revealed that only the predominant HLA-A2.1 subtype molecule was recognized by CTL 4E4. No cross-reactivity on other, biochemically related HLA-A2 population subtypes was observed, including HLA-A2.2 cells (Hill, CVE, ZYL, M7), HLA-A2.3 cells (TENJ, DK1), or HLA-A2.4 cells (CLA, KNE). This CTL clone appears to recognize a single epitope and, like monoclonal antibody counterparts, can be used to discriminate among immunogenic cellular and serologic epitopes on closely related HLA-A2 molecules. On the basis of the known sequence changes in mutant and subtype HLA-A2 molecules, it appears that the sequence spanning residues 147 to 157 may be critical for cellular recognition of this Class I MHC molecule.     

Reactivity patterns with HLA-A2 variants indicate lack of identity between determinants defined by monoclonal antibodies and cytotoxic-T-cell clones

The anti-HLA-A2 monoclonal antibodies (MoAb) CR11-351 and 4B inhibit the binding of each other to HLA-A2 lymphoid cells and block the cytotoxicity of the anti-HLA-A2 cytotoxic-T-cell clone R32. The blocking does not reflect reactivity of the MoAb CR11-351 and 4B and of the cytotoxic-T-cell clone R32 with the same determinant, since they display differential reactivity with four HLA-A2 variants which carry amino acid substitutions at different positions. These results show for the first time in the human system that Class I HLA variants represent useful reagents to compare the fine specificities of monoclonal antibodies and T-cell clones. Furthermore our data suggest that T-cell recognition depends upon the tertiary structure of the antigen.     

Monoclonal antibodies to HLA-A,B, and Ia-like antigens inhibit colony formation by human myeloid progenitor cells

Hybridomas derived from the fusion of murine myeloma cells with splenocytes from mice immunized with human cultured lymphoid cells secreted monoclonal antibodies to human cell surface antigens. Serologic and immunochemical assays showed that 4 monoclonal antibodies (Ab Q2/47, Q2/61, Q2/70, Q2/80) recognize framework determinants of Ia-like antigens and 1 monoclonal antibody (Ab Q1/28) reacts with determinants expressed on the heavy chain of HLA-A,B antigens. Both anti-HLA-A,B and anti-Ia-like antigen monoclonal antibodies caused complement-dependent inhibition of granulocyte-macrophage colony formation by human bone marrow grown in soft agar. Mixing experiments excluded the possibility of an indirect effect on progenitor cells by lysis of auxiliary cells. These results indicate that human myeloid progenitor cells express HLA-A,B and Ia-like antigens.     

Molecular characterization of HLA-A,B homologues in owl monkeys and other nonhuman primates

Mouse anti-HLA-A, B monoclonal antibodies have been used to study the homologues of HLA-A, B antigens in other primate species. Immunoprecipitates of primate histocompatibility antigens from extracts of radioactively labeled lymphocytes were analyzed by SDS-polyacrylamide electrophoresis. Primate histocompatibility antigens appear to have similar molecular structure to human HLA antigens. Owl monkeys, which react polymorphically with some monomorphic anti-HLA antibodies, showed biochemical differences which correlated with the serological polymorphism. An antibody (W6/32) which only reacts with the HLA/β ₂-microglobulin complex in humans and not with the free HLA heavy chain has the reverse specificity in some owl monkeys.     

Human cytotrophoblast populations studied by monoclonal antibodies using single and double biotin-avidin-peroxidase immunocytochemistry

Single and double biotin-avidin-peroxidase immunocytochemical methods in conjunction with an anti-trophoblast monoclonal antibody 18B/A5 and an anti-HLA-A,B,C monoclonal antibody W6/32 were used to study various human trophoblast populations. Several combinations of peroxidase substrates were tried in the double-labeling procedure. It was concluded that the use of 4-chloro-1 naphthol to develop the primary sequence peroxidase and of 3-amino-9-ethyl carbazole for the second sequence peroxidase was the most suitable. The significant findings were: Monoclonal antibody 18B/A5 proved to be a useful marker for villous as well as nonvillous trophoblast, which facilitated the identification of these cells particularly in the placental bed. The expression of MHC Class I antigens was not confined to extravillous trophoblast but these antigens were also demonstrable on the villous cytotrophoblast proliferating to form new primary villi. Double labeling revealed that many of these cells, particularly those furthest away from the mesenchymal core, expressed both trophoblast and HLA antigens as shown by a mixing of the colors produced by the two reaction products. A large number of these HLA-A,B,C, positive trophoblast cells were found to infiltrate deep into the uterine myometrium. The hypothesis was put forward that these fetal cells could be the ones that are responsible for maternal sensitization.     

Molecular analysis of HLA-A2.4 functional variant KLO: close structural and evolutionary relatedness to the HLA-A2.2 subtype

The structure of an HLA-A2.4 functional variant (A2.4c) expressed on donor KLO has been examined by comparative peptide mapping with other HLA-A2 antigens of known structure and radiochemical sequencing. All the peptide differences between A2.4c and A2.1 could be accounted for by five amino acid changes at positions 9, 43, 66, 95, and 156. The nature of residues 9, 43, and 95 in A2.4c was determined by sequencing to be identical to those in A2.2Y. The nature of residue 156 in A2.4c was also assigned as identical to that in A2.2Y on the basis of the identity of the corresponding peptide in its chromatographic comparison with A2.2Y. Position 66 was unique to A2.4c. It was determined to be an Asn residue instead of the Lys present in all other HLA-A2 antigens of known structure. This was the only detected amino acid difference between A2.4c and A2.2Y. The results indicate that, from a structural point of view, A2.4c is most closely related to the A2.2 subtype antigens and not to other A2.4 antigens. The data are compatible with the assumption that A2.4c was derived from A2.2Y by a single point mutation event.     

Modulation by cytokines of HLA antigens,intercellular adhesion molecule 1 and high molecular weight melanoma associated antigen expression and of immune lysis of clones derived from the melanoma cell line MeM 50-10

Summary Clones were isolated from the cultured human melanoma cell line MeM 50-10, which metastasizes in nude mice with a pattern similar to that in patients with melanoma. Analysis with monoclonal antibodies detected heterogeneity among the clones in the expression of HLA class I antigens, HLA class II antigens, intercellular adhesion molecule 1 and high molecular weight melanoma associated antigen. The clones MeM A16 and MeM A18 were also shown to display differential susceptibility to modulation by immune interferon (IFN-) and/or tumor necrosis factor (TNF-) of the expression of the four types of antigens analyzed. In spite of differences in the antigenic profile, the two clones did not differ in their susceptibility to lysis by lymphokine-activated killer (LAK) cells and by anti-HLA-A2 cytotoxic T cells. The increase in the expression of HLA class I antigens induced by IFN- and/or TNF- on the two clones was associated with an increased susceptibility to lysis by anti-HLA-A2 cytotoxic T cells. Because of the metastasizing properties of cultured melanoma cells MeM 50-10, the clones we have isolated, with their distinct antigenic profile and differential susceptibility to modulation by cytokines, may represent useful models to investigate the role of distinct antigenic structures in the metastatic process.This work was supported by the National Institutes of Health grants AI21384, CA37959 and CA39559     

Serological expression after sequential double transfection with purified HLA-11 gene of mouse fibroblasts carrying human beta-2 microglobulin

A genomic cosmid library constructed from DNA from a genotyped individual (JF = HLA-A11, Cw–, B38/A26, Cw7, B51) was screened for clones containing class I histocompatibility genes. Among these clones, one was found to carry a 4.8 kb Hind III fragment which is highly correlated with HLA-A11. This clone was used to transfect LMTK⁺ cultured mouse fibroblast transformants expressing human beta-2 microglobulin. The human beta-2 microglobulin heavy chain-associated determinant was positively detected by the M18 monoclonal antibody. HLA-A11 expression on these doubly transformed cells was specifically demonstrated by complement-dependent cytotoxicity with HLA-A11 + A3-specific but not with HLA-A3-specific monoclonal antibodies. Absorption studies with human alloantisera confirmed the presence on these cells of HLA-A11 determinants and of cross-reacting determinants which absorbed anti-HLA-A1 and –A3 alloantisera. The JF5-J27 transfected cell expressed both heavy and light chains of human class I histocompatibility genes.Abbreviations used in this paper ₂m beta-2 microglobulin - CTL cytolytic T lymphocytes - FCS fetal calf serum - HAT hypoxanthine-azaguanine-thymidine - kb kilobase pair - MHC major histocompatibility complex - MoAb monoclonal antibodies - PBL peripheral blood lymphocytes - PEG polyethylene glycol - r correlation coefficient This study is dedicated to the memory of Jean-Jacques Metzger.     

Cross-reactivity between human and murine lymphocyte antigens

The anti-H-2 alloantiserum D-32 [(BlO.A(2R) × C3H.SW) anti-C3H] is cytolytic to human lymphocytes. Fab₂ blocking assays, indirect immunoprecipitation and sequential immunoprecipitation experiments showed that the anti-H-2 alloantiserum D-32 recognizes antigenic determinants which are expressed on the heavy chain of subpopulations of HLA-A, B antigens. These determinants are different from those defining the serological polymorphism of the HLA-A, B, C system, are the same as or spatially close to those recognized by the anti-HLA-A, B monoclonal antibody Q6/64 and are expressed on rabbit, rat or guinea pig lymphocytes.     

Chemical, physical-chemical, and immunological properties of papain-solubilized human transplatation antigens.

Papain-solubilized HLA-A, -B, and -C antigens have been isolated from cadaveric spleens. The isolated material was homogeneous and comprised subunits with the apparent molecular weights 33,000 and 12,000. Amino acid analyses of a mixture of HLA antigen heavy chains obtained from a great number of spleens with different HLA antigen phenotypes revealed a composition that is very similar to that of individual HLA-A and -B antigens. Likewise, the NH2-terminal 30 residues of the HLA-antigen heavy chain mixture were virtually identical with that recorded for individual specificities. The circular dichroism spectra for the isolated HLA antigens and for free beta2-microglobulin revealed similarities with spectra recorded for immunoglobulin chains and domains. The HLA-antigen heavy chain may contain an appreciable amount of beta structure. Antibodies raised against free beta2-microglobulin react better with beta2-microglobulin in free form than when bound to the HLA-A, -B, and -C antigen heavy chains. This is due to the fact that free beta2-microglobulin can bind a maximum of four Fab fragments simultaneously, whereas the HLA-antigen-associated beta2-microglobulin can bind only two Fab fragments without dissociating from the heavy HLA-antigen subunit.     

Differential localization within human kidney of five membrane proteins expressed on acute lymphoblastic leukemia cells

The reactivity of a panel of monoclonal antibodies (MAb) produced against non-T, non-B acute lymphoblastic leukemia cells was investigated by immunoperoxidase staining of sections of normal human kidney. The antigens of kidney reactive with the MAb were isolated by immunoaffinity chromatography and were purified further by immunoprecipitation. Two MAb, 44D7 and 44H9, reacted with determinants found exclusively on the basolateral membranes of proximal convoluted tubules. The 44D7 antigen isolated from kidney was biochemically similar to that isolated from leukemic cells. It was resolved as a multimeric complex with an apparent m.w. of 120,000 when analyzed by SDS-PAGE under nonreducing conditions. The 44H9 antigen has not yet been purified from kidney. MAb 50B4 reacted with components of the interstitium and with the mesangium of glomeruli. It immunoprecipitated a polypeptide chain of apparent m.w. 85,000, similar to that of the 50B4 antigen isolated from leukemic cells. MAb 44G4 also reacted with the mesangium of glomeruli and with the interstitium of the kidney. However, the endothelium of glomerular capillaries and of interstitial blood vessels has also reacted with MAb 44G4. The kidney antigen recognized by MAb 44G4 was characterized as a major polypeptide band, 95,000 m.w. (reduced) and 125,000 m.w. (nonreduced), a subunit structure analogous to the 44G4 antigen isolated from leukemic cells. MAb 44E3 reacted with all cellular elements of glomeruli, tubules, blood vessels, and interstitium. Two polypeptide chains of apparent m.w. 94,000 and 90,000 were immunoprecipitated from kidney by MAb 44E3, while a single polypeptide chain of 94,000 m.w. was precipitated from leukemic cells. Our results describe five new antigens with distinctive cellular distributions within kidney.     

In vitro-isolated human cytotoxic T-lymphocyte clones detect variations in serologically defined HLA antigens

T cells of two donors, JR (HLA-A23, 29; B7,7; G; DRw5) and HG (HLA-A2, 23; B40, w44; Cw4), were stimulated with cells from an HLA homozygous lymphoblastoid cell line JY (HLA-A2, 2; B7,7, C-, DRw4, 6) and cloned by limiting dilution after the third stimulation. Two cytotoxic T-cell (CTL) clones, JR-2-16 (from donor JR) and HG-31 (from donor HG), were used for detailed studies. The results of a panel study using lymphocytes from HLA-typed individuals and a study with two HLA recombinant families indicate that the antigens recognized by the CTL clones JR-2-16 and HG-31 were highly associated with HLA-A2 and HLA-B7, respectively. Blocking studies with a monoclonal antibody recognizing a framework determinant on HLA-A, -B and-C antigens and a monoclonal antibody reacting with HLA-A2 support the notion that JR-2-16 and HG-31 interact with the HLA-A2 and the HLA-B7 antigens per se. However, these clones did not recognize the HLA-A2 and HLA-B7 of all donors typed for these antigens, suggesting that the HLA-A2 and HLA-B7 antigens of these particular donors are variants of the serologically defined HLA antigens. These results indicate that in vitro-derived human CTL clones detect variations in the serologically defined allospecificities and can be used as reagents to elucidate the polymorphism of HLA antigens further.Abbreviations used in this paper: CTL cytotoxic - T lymphocytes - BSA bovine serum albumin - PHA phytohemagglutinin - Con A concanavalin A.     

Activation of antigen-specific suppressor T lymphocytes in man involves dual recognition of self class I MHC molecules and Leu-4/T3-associated structures on the surface of inducer T lymphocytes

We showed previously that fresh Leu-2+ T cells respond to autologous antigen-primed Leu-3+ T cells by proliferation and differentiation into suppressor T cells (Ts) that specifically inhibit the response of fresh Leu-3+ cells to the original priming antigen. This study was undertaken to characterize the role of various cell surface molecules expressed by antigen-primed Leu-3+ cells in their activation of Leu-2+ Ts cells. Alloactivated Leu-3+ blasts were treated in the absence of complement with a variety of monoclonal antibodies recognizing distinct antigens on human lymphoid cells, and then were examined for their functional effects on fresh autologous T cells. Prior treatment of Leu-3+ blasts with anti-Leu-4 or anti-HLA-A,B,C framework antibodies, but not with anti-Leu-1, anti-Leu-3, anti-Leu-5, or anti-HLA-DR framework-specific antibodies, not only blocked proliferation of fresh Leu-2+ cells, it also prevented their differentiation into Ts cells. Furthermore, after their activation by Leu-3+ blasts, Leu-2+ Ts cells inhibited the response of fresh Leu-3+ cells from only those individuals who shared HLA-A,B phenotypes with suppressor-effector cells. These results suggest that both the inductive and effector phases of suppression involve dual recognition of autologous class I MHC molecules and structures associated with the Leu-4 (T3) molecule on the surface of antigen-reactive Leu-3+ cells.     

Shared human melanoma antigens. Recognition by tumor-infiltrating lymphocytes in HLA-A2.1-transfected melanomas.

Three predominantly CD8+ CTL lines, TIL 501, TIL 620, and TIL 660, were generated from three HLA-A2+ melanoma patients by culturing tumor-infiltrating lymphocytes in 1000 U/ml IL-2. These tumor-infiltrating lymphocytes lysed 12 of 18 HLA-A2+ autologous and allogeneic melanomas, but none of 20 HLA-A2-negative melanomas. They also did not lyse the MHC class I negative lymphoma-leukemia cell lines, Daudi, K562, or HLA-A2+ non-melanoma cell lines including PHA or Con A-induced lymphoblast, fibroblast, EBV-transformed B cell, Burkitt's B cell lymphoma, and colon cancer cell lines. Autologous and allogeneic melanoma lysis was inhibited by anti-CD3, by anti-MHC class I, and by anti-HLA-A2 mAb, indicating recognition of shared tumor Ag among melanoma cell lines in a TCR-dependent, HLA-A2-restricted manner. Six HLA-A2-negative melanoma cell lines obtained from five HLA-A2-negative patients were co-transfected with the HLA-A2.1 gene and pSV2neo. All 17 cloned transfectants expressing cell surface HLA-A2 molecules, but none of 12 transfectants lacking HLA-A2 expression, were lysed by these three HLA-A2-restricted, melanoma-specific CTL. Lysis of the HLA-A2+ transfectants was inhibited by anti-CD3, by anti-MHC class I, and by anti-HLA-A2 mAb, indicating recognition of shared tumor Ag on transfectants in a TCR-dependent, HLA-A2-restricted manner. These results identify the HLA-A2.1 molecule as an Ag-presenting molecule for melanoma Ag. They also suggest that common melanoma Ag are expressed among melanoma patients regardless of HLA type. These findings have implications for the development of melanoma vaccines that would induce antitumor T cell responses.     

The free and the β2-microglobulin-associated heavy chains of HLA-A,B alloantigens share the antigenic determinant recognized by the monoclonal antibody Q1/28

Serological and immunochemical assays have shown that the monoclonal antibody Q1/28 recognizes an antigenic determinant which is expressed on the heavy chain of subsets of HLA-A, B antigens and is distinct from those defining the serological polymorphism of this system. Association of the HLA-A, B heavy chain with ₂-microglobulin is not required for expression of the antigenic determinant recognized by the monoclonal antibody Q1/28, since this antibody can immunoprecipitate a 45 000 m. w. component from radiolabeled lymphoid-cell glycoproteins immunodepleted with either an anti-human ₂-microglobulin xenoantiserum or the MoAb W6/32 to framework determinants of HLA-A, B, C antigens. Furthermore, the MoAb Q1/28 can immunoprecipitate a 45 000 m. w. component from an NP40lysate of radiolabeled Daudi cells, which lack the genetic information for ₂-microglobulin. The determinant recognized by the MoAb Q1/28 is relatively resistant to denaturing treatments and does not appear to be carbohydrate in nature. The MoAb Q1/28 is the first example of an antibody which recognizes an antigenic determinant expressed on both the ₂-microglobulin-associated and free HLA-A, B heavy chains.     

Attempts at a demonstration of cross reactivity between the HLA- antigens A2 and B12 or A1 and B8

Using human anti-HLA-A1, A2, B8 and B12 sera the cross reactivity between HLA-antigens A1 and B8 or A2 and B12 respectively was investigated by means of the absorption test. A cross reactivity could be proved to exist between A2 and B12 antigens, but only with an anti-HLA-B12 serum which was adsorbed by A2 positive and B12 negative thrombocytes as well as by A2 negative and B12 positive ones. Thus, the conclusion may be drawn that this serum covers a determinant common to HLA-A2 and B12.     

Analysis of human class I antigens by two-dimensional gel electrophoresis

Class I antigens were isolated by immunoprecipitation from cell extracts prepared from mitogenically stimulated and internally radiolabeled peripheral blood lymphocytes (PLBs). The precipitating antibodies used are monomorphic and recognize a determinant on the heavy chain of HLA-A, B, C antigens regardless of their allelic specificities when complexed with ₂m, or determinants on ₂m itself. Comparison of class I molecules isolated from 25 different homozygous typing cels (HTC) and analyzed by two-dimensional (2-D) gel electrophoresis allowed the identification of those HLA-A,13 locus specificities most common in the European Caucasoid population. Class I antigens isolated from HTC that are HLA identical are biochemically indistinguishable also. Evidence was obtained for the expression of additional class I antigens besides the HLA-A, B, C locus products: for some haplotypes, up to six class I genes may be active in mitogenically activated PBLs. No differences in molecular weight and isoelectric point of the class I heavy chains were observed between the antigens recognized by W6/32, the anti-heavy chain reagent, and anti- ₂m reagents. The nature of the mitogenic stimulus, i. e., pokeweed mitogen or phytohemagglutinin, was irrelevant with respect to the class I antigens isolated by this method. Using the HTCs as reference, a panel of HLA-B27 positive heterozygous cells was analyzed. Two types of HLA-B27 antigens, distinct by CML typing were represented. These two forms differed also in their biochemical properties. In addition, we obtained evidence for the existence of an A2 variant. This finding was likewise confirmed by CML typing.