Two distinct class II molecules encoded by the genes within HLA-DR subregion of HLA-Dw2 and Dw12 can act as stimulating and restriction molecules

By using two-dimensional polyacrylamide gel electrophoresis (2D-PAGE), we investigated the difference in the HLA class II molecule between HLA-Dw2 and Dw12, both of which are typed as HLA-DR2 serologically. The anti-HLA-DR framework monoclonal antibody (MoAb) HU-4 precipitated an alpha-chain and two beta-chains of human class II molecules from both Dw2 and Dw12 homozygous B lymphoblastoid cell lines. It was demonstrated clearly that an alpha-chain (alpha 1) and one of the beta-chains (beta 1) showed no difference in mobility in the 2D-PAGE between Dw2 and Dw12, but that another beta chain (beta 2) of Dw2 was distinct from that of Dw12 in the 2D-PAGE profile. Thus, MoAb HU-4 precipitated alpha 1 beta 1 and alpha 1 beta 2 molecules from Dw2 and Dw12, and the alpha 1 beta 1 molecule appears to be an HLA-DR2 molecule. The alpha 1 beta 2 molecule, on the other hand, is a class II molecule distinct from those precipitated with anti-DR2, anti-DQw1 (DC1, MB1, MT1), or anti-FA MoAbs. MoAb HU-4 completely inhibited the mixed lymphocyte culture reaction (MLR) between Dw2 and Dw12, but anti-DR2 MoAb HU-30, which reacts only with the alpha 1 beta 1 molecule, did not show an inhibitory effect on the MLR between Dw2 and Dw12. The alpha 1 beta 2 molecule is therefore the molecule which elicits MLR between Dw2 and Dw12. An IL 2-dependent T cell line established from an HLA-Dw12/D blank heterozygous high responder to the streptococcal cell wall antigen (SCW) clearly distinguished the Dw2 specificity from Dw12 specificity expressed on the antigen-presenting cell (APC). Moreover, MoAb HU-4 markedly inhibited the cooperation between the T cell line and APC to respond to SCW. These observations indicate that the alpha 1 beta 2 molecule is recognized as a restriction molecule by the T cell line at the antigen presentation of SCW through APC MoAb HU-30 on the other hand partially inhibited the MLR between Dw2 or Dw12 homozygous cell as a stimulator cell and non DR2 cell as a responder cell. It markedly inhibited the proliferative response of the Dw12/D- heterozygous T cell line to SCW, presented by Dw2+ but Dw12- allogeneic APC, and the peripheral response of Dw2 or Dw12 homozygous peripheral blood lymphocytes to SCW. Thus, two distinct class II molecules encoded by the genes within the HLA-DR subregion of HLA-Dw2 and Dw12 can act as stimulating molecules in the MLR and as restriction molecules in the antigen presentation by APC.     

Evidence for polymorphism of MB3 antigens among three HLA-D clusters associated with HLA-DR4

In a previous study, we showed that the three hitherto serologically indistinguishable HLA-D specificities associated with HLA-DR4, HLA-DYT, HLA-DKT2, and HLA-Dw4 can be distinguished on the basis of their reactivity with two distinct la-like-specific monoclonal antibodies, HU-18 and HU-23. In this study, we attempted to identify and characterize Ia-like molecules recognized by HU-18 and HU-23 on a molecular level because la subsets (HLA-DR, MB, MT, or SB) identified by them remained unknown. The results of sequential coprecipitation assays and two-dimensional gel analyses showed that both HU-18 and HU-23 recognize antigenic determinants borne on M133 but not on HLA-DRw6.2 molecules. Because the two monoclonal antibodies, specific for determinants carried on MB3 molecules, show distinct reactivity against homozygous typing cells defining HLA-DYT, HLA-DKT2, and HLA-Dw4, all of which share DR4-MB3, the data indicate that these three HLA-D clusters associated with HLA-DR4 possess distinct MB3 molecules, suggesting the existence of polymorphism in MB3 antigens.     

Nonrandom selection of T cell specificities in anti-HLA-DR responses. Sequence motifs of the responder HLA-DR allele influence T cell recruitment

The self-restriction of Ag-specific T cell responses is interpreted as the result of a positive selection of the individual's T cell specificities for their compatibility with self-MHC molecules. If the T cell receptor (TCR) specificities in any given individual have an affinity for syngeneic MHC molecules, it is unclear how they interact with allogeneic MHC structures. To approach this question, we analyzed 123 alloreactive HLA-DR4 Dw4 or Dw14 specific T cell clones that were generated from responder/stimulator combinations with defined disparities in the HLA-DR beta 1-chain. Sets of T cell clones were established from three different HLA-Dw4+ responders and compared for their fine specificities. The majority of HLA-DR4 Dw14 specific T cell clones co-recognized HLA-DR1 Dw1+ (33 to 36% of all T cell clones) or HLA-DRw14 Dw16+ (26 to 33%) stimulators, both of which share very similar sequences in the third hypervariable region of the HLA-DR beta 1-chain with the HLA-DR4 alleles Dw4 and Dw14. These data suggest that sequence and structural similarities in the alpha-helical portions of the HLA-DR molecule impose a strong bias on the recognition of allotargets. The second haplotype of the responder did not appear to affect the typical fingerprint of T cell recognition except for the deletion of self-reactive TCR specificities. Nonrandom usage of TCR specificities in anti-HLA-DR responses was also found for HLA-DRw11/DRw13+ and HLA-DRw11/DR7+ T cell donors who did not share any obvious polymorphic sequence stretches with the allostimulators HLA-DR4 Dw4 or Dw14. T cell clones from an HLA-DRw11/DRw13+ responder functionally resembled the TCR specificities derived from the HLA-DR4 Dw4+ donors. T cell clones derived from an HLA-DRw11/DR7+ individual were characterized by a distinct cross-reactivity pattern preferring HLA-DRw13 Dw19+ (50 to 60%) and HLA-DR3+ (43 to 57%) stimulator cells. These findings suggest that the responder HLA-DR alleles influence the structural constraints in the recognition of allo-HLA-DR molecules in closely related and in completely disparate responder/stimulator combinations.     

Serologic dissection of HLA-D specificities by the use of monoclonal antibodies

Three cytotoxic monoclonal antibodies, HU-11, HU-32, and HU-33, specific for human Ia-like antigens were used to analyze the two HLA-DR2-associated HLA-D specificities, HLA-Dw2 and HLA-Dw12. In the HLA-Dw2, DR2, MB1 homozygous B-cell line EB-CMG, the binding of radiolabeled HU-32 and HU-33 was strongly inhibited by the addition of nonlabeled HU-11, whereas no inhibition occurred in the HLA-Dw12, DR2, MB1 homozygous B-cell line EB-KT. To confirm this differential inhibition pattern further, F(ab')2 fragments were prepared from HU-11, and their ability to inhibit complement-dependent lysis mediated by HU-32 and HU-33 was assessed against a total of five homozygous typing cell lines homozygous for HLA-Dw2, DR2, MB1 or HLA-Dw12, DR2, MB1, including EB-CMG and EB-KT. Here again, the same differential inhibition pattern as that observed in the radiobinding inhibition assays was obtained. Thus, the data suggest that the two kinds of HLA-DR2-positive homozygous typing cell lines with distinct HLA-D specificity can be distinguished from each other by using solely serologic methods. This is the first clear-cut serologic distinction made between homozygous typing cells defining HLA-Dw2 and those defining HLA-Dw12, since no serologic means that enables one to distinguish one from the other has been available.     

Serologic dissection of HLA-D specificities by the use of monoclonal antibodies

To study the gene products of the HLA complex, we produced two monoclonal antibodies, termed HU-18 and HU-23. They were active in complement-dependent cytotoxicity and detected B-cell alloantigens encoded by a locus (or loci) linked to HLA. When three types of HLA-DR4 homozygous B-cell lines with different HLA-D specificities were tested for reactivity with HU-18 and HU-23, they displayed distinct reaction patterns depending on the HLA-D specificities they possessed: EBV-Wa (HLA-DYT homozygous), negative for both HU-18 and HU-23; KT2 and KOB (HLA-DKT2 homozygous), positive only for HU-18; and ER (HLA-Dw4 homozygous), positive for both. These differential reaction patterns were further confirmed by testing against a panel of 17 HLA-DR4-positive peripheral blood lymphocytes with known HLA-D specificities. Thus, these monoclonal antibodies allow us to identify HLA-DYT, HLA-DKT2, and HLA-Dw4 solely by serologic methods. This is the first clearcut serologic identification of these three HLA-DR4-associated HLA-D specificities, which have been indistinguishable by conventional serology and identified only by cellular techniques. It is hoped that immunochemical investigations using HU-18 and HU-23 will advance our understanding of the HLA-D region on a molecular level.     

Immunochemical analysis of the Ia polymorphisms among the family of DR7-associated HLA-D specificities

Among cells that bear the serologically defined Ia alloantigen DR7, four T cell-defined HLA-D specificities have been described: Dw7, Dw17, Dw11, and Dw7L. Ia molecules expressed by cells homozygous for these specificities have been compared by using immunofluorescence and two-dimensional gel electrophoresis in order to identify the DR and DQ polymorphisms among the family of DR7-associated HLA-D specificities. Cells homozygous for each of the four HLA-D specificities have in common one DR molecule that is indistinguishable by these methods. Two DR-specific monoclonal antibodies, IIIE3 and 109d6, detect a second distinct DR molecule on Dw7, Dw17, and Dw7L cells. This second DR molecule is also very similar from cells of the three specificities. In contrast, a second DR molecule was not detected on four Dw11 homozygous cells. Therefore, these data raise the possibility that all DR homozygous cells do not express the same number of DR molecules. The DQ molecules expressed by DQw2-positive Dw7, Dw17, and Dw7L cells are also very similar, whereas DQw3-positive Dw11 DQ molecules are structurally different. Therefore, no DR or DQ structural polymorphisms were detected to correlate with the Dw7, Dw17, and Dw7L T cell-defined Ia polymorphisms.     

Highly polymorphic products of both HLA-DR and HLA-DQ genes contribute to the polymorphism of the HLA-DR w13 haplotype

We studied the polymorphisms of HLA-DR and HLA-DQ products from HLA-DRw13 haplotypes by analyzing the restriction of influenza A-specific cloned T cells from an HLA-DRw13,DQw1,Dw19 homozygous individual. The results show that (1) some functional epitopes, which can be borne by either HLA-DR or HLA-DQ molecules, are strictly correlated with the HLA-Dw19 subtype of HLA-DRw13. This clearly indicates that both HLA-DR and HLA-DQ products contribute to the HLA-Dw19 subdivision of HLA-DRw13. (2) At least two different restricting epitopes are borne by DR products: one is correlated with the HLA-DRwl3 serologically defined specificity, which includes Dw19 and Dw18 haplotypes; the other is correlated with the only HLA-Dw19 subtype of HLA-DRwl3. (3) Restricting epitopes borne by DQ molecules have been found on Dw19 cells only. (4) DQ-restricted clones were unable to react with DQwl APC of any other haplotypes tested, including DR1, DR2-long, DR2-short, and DRw14, demonstrating a high degree of functional polymorphism among the serologically defined DQw1 specificities.Abbreviations used in this paper: APC antigen-presenting cells - cpm count per minute - HAU hemagglutinin units - IL-2 interleukin 2 - MHC major histocompatibility complex - mAb monoclonal antibody - PBM peripheral blood mononuclear cells - PHA phytohemagglutinin - pl isoelectric point - PMA phorbol myristic acetate - SD standard deviation     

The polymorphisms of HTC-defined HLA specificities in the Shanghai Chinese population

With reference sera and homozygous typing cells (HTCs) of 3rd Asia-Oceania Histocompatibility Workshop Conference, 56 healthy unrelated subjects in Shanghai were typed for HLA-A, B, C, DR, DQ, and Dw. This paper presents the results of HLA-Dw typing, its relationship to serological class II antigens, and the distribution of Dw in the population. The polymorphism patterns of Chinese Dw specificities were quite different from those in Caucasoids and Japanese. The predominant Dw phenotypes detected in Shanghai Chinese were Dw 2, Dw 3, DKT 2, Dw 7 c, (Dw7 + Dw 17) and Dw 23 (DB 5). And significant correlations were observed between Dw 1 and DR 1, Dw 2 and DR 2, Dw 3 and DR 3, Dw 7 c and DR 7, DB 7 and DRw 8, as well as Dw 23 and DR 9. SMY 129, a novel Dw specificity defined by local HTCs and co-studied by the laboratories joined for Dw typing in 3rd AOHWC showed its correlation with DR 5. Nevertheless, more than fifty percent of Dw specificities could not be assigned in the four correspondent designated serological antigens, DR 2, DR 5, DRw 8 and DR 9, respectively, which, together with other blank Dw specificities, gave a total blank Dw gene frequency as high as 43.2% in the population. It was suggested by further analysis that novel Dw specificities might be identified more effectively if efforts would be concentrated on DR 5 and DR 9, two antigen families which, in some way, might represent the characteristics of HLA system in Chinese. Besides, certain HTC-defined antigens, e.g. Dw 3 and the DR 4-related Dw specificities, have been revealed to be in linkage disequilibrium with other DR antigens in addition with the correspondent designated ones, resulting in some unique haplotype combinations in Shanghai Chinese. It seems to us that the particular patterns of polymorphisms of serum- and cell-defined HLA class II antigens would be helpful to elucidate the mechanisms by which certain diseases are in association with HLA in Chinese in a different manner as compared with that in Caucasoids.     

HLA-DQ-restricted CD4+ T cells specific to streptococcal antigen present in low but not in high responders.

We have found that the low immune response to streptococcal cell wall Ag (SCW) was inherited as a dominant trait and was linked to HLA, as deduced from family analysis. In the present report, HLA class II alleles of healthy donors were determined by serology and DNA typing to identify the HLA alleles controlling low or high immune responses to SCW. HLA-DR2-DQA1*0102-DQB1*0602(DQw6)-Dw2 haplotype or HLA-DR2-DQA1*0103-DQB1*0601(DQw6)-DW12 haplotype was increased in frequency in the low responders and the frequency of HLA-DR4-DRw53-DQA1*0301-DQB1*0401(DQw4)-Dw15 haplotype or HLA-DR9-DRw53-DQA1*0301-DQB1*0303(DQw3)-Dw23 haplotype was increased in the high responders to SCW. Homozygotes of either DQA1*0102 or DQA1*0103 exhibited a low responsiveness to SCW and those of DQA1*0301 were high responders. The heterozygotes of DQA1*0102 or 0103 and DQA1*0301 showed a low response to SCW, thereby confirming that the HLA-linked gene controls the low response to SCW, as a dominant trait. Using mouse L cell transfectants expressing a single class II molecule as the APC, we found that DQw6(DQA1*0103 DQB1*0601) from the low responder haplotype (DR2-DQA1*0103-DQB1*0601(DQw6)-Dw12) activated SCW-specific T cell lines whereas DQw4(DQA1*0301 DQB1*0401) from the high responder haplotype (DR4-DRw53-DQA1*0301-DQB1*0401(DQw4)-Dw15) did not activate T cell lines specific to SCW. However, DR4 and DR2 presented SCW to CD4+ T cells in both the high and low responders to SCW, hence the DR molecule even from the low responder haplotype functions as an restriction molecule in the low responders. Putative mechanisms linked to the association between the existence of DQ-restricted CD4+ T cells specific to SCW, and low responsiveness to SCW are discussed.     

HLA class II restriction of T helper cell response to cytomegalovirus (CMV). I. Immunogenetic control of restriction

All three HLA class II families (DR, DQ, and DP) are involved in restriction of helper T cell (Th) recognition of nominal antigens including CMV. Only limited studies have been described previously to determine whether restricting determinants of DR and especially DQ are subtypic to the serologically defined DR and DQ specificities, and to what extent restricting determinants are associated with Dw specificities defined in alloresponses. In the present report, we describe a large number of CMV-specific Th clones derived from two different individuals who are seropositive for CMV. Clones were classified as being DR-, DQ-, or DP-reactive based on blocking with monoclonal antibodies. DR- and DQ-restricted clones were then examined in panel studies using antigen-presenting cells (APC) expressing the Dw subtype of the restricting DR-DQ haplotype, as well as APC expressing different Dw subtypes associated with the serologically defined specificity. Unrelated specificities were also included. Our findings show that not only for DR but for DQ as well, the primary restricting determinants appear to be subtypic to the serologically defined antigen; furthermore, subtype restriction for both DR and DQ is very closely associated with single Dw specificities. In several cases in which cross-reactivity among restricting Dw specificities was observed in association with a given DR or DQ haplotype, a molecular basis could be suggested to explain the cross-reacting determinants. A small minority of the clones appeared to be CMV specific, but was restricted by a determinant(s) that is either monomorphic or minimally polymorphic.     

Detection of a novel HLA-DQ specificity: serological and immunochemical analyses by a monoclonal antibody

A monoclonal antibody (mAb) with a novel human B-cell allospecificity was produced by immunizing a C3H/He mouse with the human B lymphoblastoid cell line EBV-Wa (HLA-DR4/Dw15/DQblank homozygous). The mAb, termed HU-46, reacted with B cells from not only DR4/Dw15-positive individuals but also certain DRw8/Dw8-positive ones whose DQ phenotypes had not yet been defined. Two-dimensional gel analyses indicated that the mAb recognized class II antigens which were encoded by the HLA-DQ locus. Furthermore, in genetic analysis, the gene encoding the class II antigen detected by HU-46 met the Hardy-Weinberg condition as a fourth allele of the DQ locus. We provisionally labeled this novel DQ specificity DQWa.     

Purified HLA class II peptide complexes can induce adherence and activation of peptide-specific human T cell clones.

An initial event in T cell activation is the specific adherence of T cells via their T cell receptor to the MHC peptide complex. We have studied this adherence by incubating T cells with preformed HLA DR4Dw4 peptide complexes attached to a solid support. Adherence of sodium 51Cr-labeled T cell clones specific for the influenza hemagglutinin peptide, HA 307-319, was maximal after 15 min and was specific for the HLA DR4Dw4-HA 307-319 complex. The binding was temperature dependent and could be blocked with azide or protein kinase C inhibitors, indicating that for adherence the T cells need to be metabolically active and have a functioning protein kinase C pathway. The adherence could be blocked with CD4- or CD3-reactive murine mAb, suggesting that the TCR and CD4 molecules work in concert to induce strong adherence to the HLA DR4Dw4-HA 307-319 complex. A subsequent event in T cell activation is proliferation, which is thought to need additional proteins such as IL-1 or other adhesion molecules. MHC peptide complexes coated on microtiter plates also induced proliferation in the human T cell clones. Removal of any monocytes by treatment of human T cell clones with anti-CD14 in conjunction with C, followed by purification over a nylon wool column, did not abrogate proliferation. After prolonged culture of the T cell clones in plates coated with peptide-pulsed HLA DR4Dw4 in the presence of IL-2, the T cell clones continued to proliferate in response to peptide. These results suggest that human T cell clones do not require a second signal from a monocyte or other APC to proliferate.     

Functional definition of HLA-DR and -DQ epitopes specific for DR2-short,DwFJO haplotype

T-lymphocyte clones specific for the influenza A/Texas virus were obtained by limiting dilution of activated T cells from an HLA A2/3, B7/39, Cw -/-, DR2-short/2 short, DQw1/w1, DwFJO/FJO donor. Among the proliferating clones studied, and irrespective of their antigenic specificities, most of them were restricted by epitope(s) on HLA-DR molecules present only on DR2-short/DwFJO cells but not on DR2-negative or DR2-long positive (Dw2, Dw12, Dw-) cells. Two clones were restricted by epitopes borne by DQ products. Here again, these epitopes were present on DR2-short/DwFJO but not on DR2-long, DQw1 (Dw2, Dw12) cells, indicating that the DQwl molecules of DR2-long and DR2-short haplotypes are different. Taken together, these results indicate that the DR2-short, DwFJO haplotype is characterized by both HLA-DR- and DQ-specific molecules. Finally, one clone was restricted by an epitope shared by DR products from DR2 short/DwFJO, DRw11, and DRw13 haplotypes. This latter functional determinant has never been described until now.Abbreviations used in this paper APC antigen-presenting cells - HAU hemagglutinin units of influenza virus - HLA human leukocyte antigens - HTC homozygous typing cells - IL-2 interleukin 2 - mAb monoclonal antibody - MHC major histocompatibility complex - MLR mixed lymphocyte reactions - PBM peripheral blood mononuclear cells - %RR relative response percent     

Serological discrimination of DR4 haplotypes by radioimmunoassay

Three new alloantigenic specificities of human major histocompatibility complex class 11 molecules have been defined by testing the reactivity of alloantisera at the molecular level. Two of these specificities identify different DR4 haplotypes. The Fe75 specificity is associated with the DR4/DW10 haplotype and the CBC/MRG6 specificity with the DR4/DKT2 haplotype. Both are supertypic specificities and are associated with other DR specificities as well. Both specificities are carried by class 11 molecules belonging to the first DR subset. Together with previously described determinants, these specificities contribute to serological discrimination of the different DR4 haplotypes.     

Analysis of the HLA-DRw8 haplotype: Recognition by HTC typing of three distinct antigen complexes in Caucasians,Native Americans,and Orientals

We have used seven HLA-D homozygous typing cells (HTC) in a comparative study of the DRw8 antigen complex in three racial groups. Three distinct HLA-D specificities were recognized, each associated with HLA-DRw8. Four of the HTC defined a DRw8-associated HLA-D specificity designated 8.1, one defined a specificity designated 8.2, and two defined a specificity designated 8.3. Each of the three specificities showed an association with a distinct racial group: Dw"8.1" in Caucasians, Dw"8.2" in Pacific Northwest Indians, and Dw"8.3" in Orientals. An informative primed lymphocyte (PLT) cell generated against a Dw"8.1" haplotype was able to distinguish 8.1 from 8.2 and 8.3. Using selected anti-DRw8 sera, a serologic distinction between 8.1 and 8.3 could also be made. It was thus possible, by using both cellular and serologic techniques in a comparative population study, to recognize at least three HLA-D-defined splits of the DRw8 haplotype.     

Biochemistry of HLA-DRw6: evidence for seven distinct haplotypes

The DRw6 specificity, which has a frequency of 11% in the Caucasian population, cannot be positively defined, since no monospecific allo-antiserum is available. This particular status among DR specificities led us to study the DRw6 haplotypes at the molecular level. We performed 2D-PAGE analysis of HLA-DR molecules in 44 different DRw6 haplotypes. The data were obtained from six homozygous typing cells, eight families informative for the segregation of the DRw6 haplotype, and 15 unrelated donors. Five unique beta-chain electrophoretic patterns were detected, indicating the existence of five structurally distinct DRw6 beta-chains. Each haplotype expresses one or two beta-chains. The different combinations of the DR beta-chains present in a single haplotype allow to characterize seven unique DRw6 haplotypes. In contrast to what has been previously found for DR2 and DR4, there is no DR beta-chain common to all the DRw6 cells. Correlation of the biochemical data with the recent serologic (DRw13 vs DRw14) and cellular (Dw9, Dw18, Dw19) splits of the DRw6 specificity will be discussed.     

Demonstration of structural polymorphism among MB3 light chains by two-dimensional gel electrophoresis

The heavy and light chain subunits of MB3 molecules were isolated from KT2 (DKT2, DR4, MB3 homozygous), ER (Dw4, DR4, MB3 homozygous), JMe (Dw5, DR5, MB3 homozygous), EBV-Sh (DSh, DRw6.2, MB3 homozygous), and EBV-Ky (DKy, DRw9, MB3 homozygous) cells and were compared with one another by two-dimensional gel electrophoresis. The MB3 light chains from KT2, ER, and EBV-Ky cells were clearly different in terms of their isoelectric points, whereas those from ER, JMe, and EBV-Sh cells were indistinguishable. No differences in charge or m.w. were noted for the MB3 heavy chains from the five cell lines. Thus, three out of the five MB3-positive, D/DR-disparate cell lines were found to express structurally distinct MB3 molecules, demonstrating that MB3 is a public serologic specificity shared by at least three structurally distinct MB (human I-A-like) molecules. Because the DR light chain subunits isolated from EBV-Wa, KT2, ER, JMe, EBV-Sh, and EBV-Ky cells differed from one another in their isoelectric points, the DR light chains were apparently more polymorphic than the MB3 light chains.     

Mutations in the third, but not the first or second, hypervariable regions of DR(beta 1*0101) eliminate DR1-restricted recognition of a pertussis toxin peptide.

We have examined the role of 12 polymorphic residues of the beta-chain of the HLA-DR1 class II molecule in T cell recognition of an epitope of pertussis toxin. Murine L cell transfectants expressing wild-type or mutant DR1 molecules (containing single amino acid substitutions in DR(beta 1*0101)) were used as APC in proliferation assays involving nine DR1-restricted T cell clones specific for peptide 30-42 of pertussis toxin. Four different patterns of recognition of the mutants were found among the pertussis-specific clones. Residues in the third hypervariable region (HVR) of DR(beta 1*0101) are critically important for all the T cell clones; amino acid substitutions at positions 70 and 74 abrogated recognition by all of the T cell clones, and substitutions at positions 67 and 71 eliminated recognition by most of the clones. In contrast, most single amino acid substitutions in the first and second HVR, predicted to be located in the floor of the peptide binding groove, had little or no effect on the proliferative responses of these clones. However, the involvement of beta-chain first and second HVR residues was demonstrated by the inability of transfectants expressing wild-type DR(beta 1*0404) (DR4Dw14) or DR(beta 1*1402) (DR6Dw16) to present peptide to these clones. These beta-chains have completely different first and second HVR compared with DR(alpha,beta 1*0101) although the third HVR are identical. These results illustrate the functional importance of third HVR residues of DR(beta 1*0101) and allow definition of the molecular interactions of the DR1 molecule with the 30-42 peptide.     

Expression of the human MHC, HLA-DQW6 genes alters the immune response in C57BL/6 mice

In an attempt to obtain direct evidence for the critical role of HLA class II molecules in regulating the immune response, genomic genes for alpha- and beta-chains of HLA-DQw6 from HLA-Dw12 haplotype were introduced into the C57BL/6 (B6) strain of mouse and a line of HLA-DQw6 transgenic mouse was obtained. Tissue specificity of the expression of the transgenes was much the same as that of murine I-Ab genes. DQw6 molecules were expressed on B cells and macrophages in spleen cells and about 30 to 40% of the I-Ab+ spleen cells were positive for DQw6. The HLA-DQw6 transgenic B6 mouse became tolerant to the DQw6 molecules, as evidenced by the MLR and antibody production specific to the DQw6 molecules. The HLA-DQw6 transgenic B6 mouse showed a strong immune response to streptococcal cell wall antigen (SCW), whereas the B6 mouse was a low responder to SCW. The SCW-specific T cell line was established from the transgenic mouse and this T cell line recognized SCW in the context of HLA-DQw6 molecules expressed on the mouse L cell transfectant or on human monocytes. The proliferative response to SCW of primed lymph node T cells and the SCW-specific T cell line derived from the transgenic mice was inhibited by anti-HLA-DQ mAb. Thus, it is clear that the HLA-DQw6 genes acted as major histocompatibility genes in these transgenic mice.     

Serological typing of HLA-D: Predictive value in mixed lymphocyte cultures (MLC)

Locally produced antisera and antisera received through the Seventh International Histocompatibility Workshop exchange were investigated for specific B-cell cytotoxic activity in a panel of 95 unrelated HLA-D-typed donors. A number of sera formed clusters defining eight B-cell specificities which were strongly associated (p<0.001) to the HLA-D determinants Dw1–8. In panel investigations, only four triplets occurred. In five HLA recombinant families, these B-cell specificities followed the HLA-B-D chromosomal region, and in one —B/D recombination, DRw1 traveled with —Dw1. In MLCs between panel donors sharing zero, one, or two HLA-D-related B-cell specificities, significantly weaker MLC stimulation was observed with increasing compatibility, the median relative responses being 100, 52, and 17 percent, respectively. It is concluded that B cell-specificities HLA-DRw1–7 and WIA8 are probably coded for by HLA-D; they are excellent markers for the HLA-D determinants, which can thus be typed for by serological means; and serological typing for HLA-D has great value in predicting the outcome of MLCs.