MHC class II restricted self-recognition after allostimulation: clonal analysis

After allostimulation in vitro using a combination of HLA-A, B, C, DR, DQ, D identical but HLA-DP different homozygous typing cells, 34 T cell clones were derived. Thirty-one of them were alloreactive clones, but three clones were found to be autoreactive. One of these autoreactive clones was further expanded. In order to characterize in more detail the determinant restricting the autologous response, a panel of HLA-typed peripheral blood mononuclear cells (PBMC) or Epstein-Barr virus lymphoblastoid cell lines (EVB-LCL) was typed. A good correlation of typing responses with the self haplotype HLA-A1, B8, Cw7, DR3, DRw52, DQw2 was found. Typing responses also segregated together with this haplotype in informative families. Blocking studies using MHC class I and II specific monoclonal antibodies (MoAb) linked the restricting determinant to MHC class II molecules. The clone which was both autoproliferative and autocytotoxic bore the CD3(+), CD4(+), CD8(-), Ia(+) phenotype. Antibiotics or foreign plasma proteins were ruled out as restricted determinants.     

Autoreactive T cells in rheumatic disease. II. Function and specificity of an autoreactive T helper cell clone established from a HLA-B27+ reactive arthritis

T cell lines were established by limiting dilution of peripheral blood (PBL) and synovial fluid lymphocytes (SFL) of a patient with HLA-B27+ reactive arthritis. Among these cell lines, the CD4 phenotype was dominant. Functionally, the majority of these cell lines exhibited helper activity for the immunoglobulin production by autologous B cells and proliferated in response to autologous mononuclear cells. In most cases, this autoreactive response was associated with alloreactivity. Only one cell line, the autoreactive CD4+ T cell clone, UA-S2, which was derived from the synovial fluid, proliferated in a highly specific manner in response to a determinant associated with MHC class II products present on autologous mononuclear cells. The restriction element was shown to be associated with DR molecules by inhibition experiments with monoclonal antibodies. Within the patient's family, the capacity of mononuclear cells to stimulate a proliferative response of UA-S2 segregated together with the HLA haplotype A2 or 32, B27, Cw1, DRw11 which was contributed by the patient's mother. UA-S2 proved to be a functional helper T cell clone. In the absence of additional antigen or mitogen, it induced IgG and IgM synthesis of autologous and family members' B cells. This helper activity of UA-S2 showed the same MHC restriction as the proliferative response. Although the patient's father also typed DRw11, this haplotype was not recognized by UA-S2. It is suggested that this autoreactive T cell clone detects a microheterogeneity of the serologically defined DRw11 haplotype. Indeed, typing of the patient's family members with cellular reagents established a difference between the two DRw11 haplotypes.     

CD4+T cells restricted by DQ not by DR support CD8+T cells to grow

Much attention has been paid whether there are any differences in regulating the human immune response between HLA-DR and -DQ molecules encoded by the genes within the HLA class II multigene family. Previous studies have suggested that HLA DQ molecules control low responsiveness through activating CD4 T cells which generate CD8 positive T cells, whereas HLA -DR molecules control high responsiveness through activating CD4 helper T cells. To examine this model we investigated the streptococcal cell wall antigen (SCW) specific T cell lines restricted by either DR or DQ molecule. To identify the restricting molecules, L cell transfectants expressing DQw1, DR2AB1 or DR2AB5 from Dw12 haplotype or DQw4, DR4 or DRw53 from DW15 haplotype were used. 1. From individuals with Dw12 which is a low responder haplotype to SCW, T cell clones specific to SCW and restricted by HLA-DQw1 or DR2 were identified, whereas from individuals with Dw15 which is a high responder haplotype, only DR4 or DRw53 restricted T cell clones were identified and DQw4 restricted T cells were never observed. 2. SCW specific CD4 T cells restricted by DQw1 were able to support the growth of CD8 positive cells, whereas those restricted by DR4 could not do so. 3. The CD8 T cells also required autologous antigen presenting cells and SCW to grow, and they completely blocked the immune response to SCW in vitro. These observations clearly demonstrated the distinct function of HLA-DQ and -DR molecules in regulating the human immune response to SCW.     

T cells specific for different antigens express different HLA-D region products

T cell lines and clones were analyzed for surface expression of Ia antigens using monoclonal antibodies (mAb) that detect monomorphic and polymorphic epitopes on Ia molecules encoded by the HLA-DR and HLA-DQ gene clusters. All mAb bound to B lymphocytes or lymphoblastoid cell lines of the same individuals from whom the T cells were derived. Three mAb detecting monomorphic epitopes, primarily associated with HLA-DR, bound to all T cells showing that each clone or line expressed some type of Ia. Three other mAb defining polymorphic epitopes associated with HLA-DR products showed differential binding patterns. Two reagents, R3 and E15/4 recognizing the supertypic specificity DRw52 (formerly MT2), bound to every alloreactive clone, whereas the 16.23 mAb, detecting a private DR3-associated epitope, failed to bind to any clone. In contrast, the 16.23 epitope was detected on high percentages of T cells specific for purified protein derivative of tuberculin (PPD) or tetanus toxoid (TT). Biochemical studies showed that the 16.23 and DRw52-like epitopes can be present on distinct DR molecules on B cell lines and this may also be the case for T cells. Three other mAb, detecting epitopes associated with HLA-DQ, also revealed differential binding patterns when tested on various T cells. Two failed to bind to any alloreactive clone and to only low numbers of PPD- or TT-specific T cell lines, whereas the third bound distinctly to a CD4+/CD8+ alloreactive clone. Biochemical analyses have shown that these DQ epitopes can be present on different molecules. Combined, these observations indicate that differential expression of Ia molecules encoded by both HLA-DR and DQ occurs between B and activated T cells as well as among T cell populations of the same individual. Whether these differences reflect quantitative variations in expression of given DR or DQ molecules or, alternatively, are due to differential class II gene expression in activated T cells remains to be determined.     

Importance of HLA-DQ and -DP restriction elements in T-cell responses to soluble antigens: mutational analysis

We describe a new approach to delineating the restriction elements used by antigen-specific human T-cell lines. EBV-transformed B cell lines and congenic HLA class II antigen-loss mutants are used to present soluble antigen to immune T cells. In this way it is possible to assess the independent contribution of individual class II loci to the restriction repertoire of the T cells. In contrast to results obtained with other methods of restriction element analysis, we find that approximately 40% of the T-cell response to several antigens is restricted by non-DR class II molecules. Both mutational analysis and blocking by class II specific monoclonal antibodies demonstrate that the non-DR restricted responses derive from DQ and DP-encoded determinants. We also find specific DR/DQ haplotype preferences for the presentation of some but not all antigens. Using a mutant that expresses only the DQ1 molecule, and is derived from a DR1, DQ1 parent line, we demonstrate a functional split of serologically defined DQ1 molecules consistent with the electrophoretic variation reported between DQ1 molecules linked to DR1 and those linked to DR2. Pairs of mutants that differ by expression of a single class II protein reveal a much broader use of available class II restriction elements than previously recognized.     

Demonstration of the requirement for self antigen in the activation of autoreactive T cells.

An HLA-DR4-restricted T cell clone (26G11), which was reactive to autologous non-T cells without any nominal antigens, was established from an unimmunized normal subject that was DR1/4 positive. The reactivity of the clone was examined against L cells (LDR4) transfected with the particular DR4 genes obtained from the same subject. 26G11 cells proliferated slightly in response to LDR4 cells, but the proliferation was markedly augmented by the addition of cell lysate from an autologous B cell line. In addition, 26G11 cells killed LRD4 cells sensitized by preincubation with the cell lysate more efficiently than LDR4 cells without treatment. When LDR4 cells were preincubated with cell lysate from allogenic B cell lines, effective killing of the target cells by clone 26G11 was also observed. These data strongly suggest that this autoreactive T cell clone (26G11) recognizes endogenous antigen in the context of the DR4 molecule. This directly demonstrates the requirement for self antigen in the activation of human autoreactive T cells from a normal subject.     

Functional difference between HLA-DR and HLA-DQ molecules in mixed lymphocyte reaction

In order to analyze the functional differences between HLA-DR and HLA-DQ molecules, we have established transfectants expressing HLA class II molecules. We investigated the contribution of these molecules in mixed lymphocyte reaction (MLR) using these transfectants. 1) The genomic clones encoding for DR alpha, DR beta, DQ alpha, and DQ beta from HLA-Dw 15 haplotype were isolated. These genes were introduced into murine L cells and two kinds of stable transfectants expressing either of HLA-DR4 and HLA-DQw4 were established. Expression of HLA class II molecules on transfectants was confirmed by FACS analysis using monoclonal antibodies specific for HLA class II molecules. 2) Primary MLR against class II transfectants and blocking experiments showed that DR molecules function as dominant stimulator molecules in allo MLR, whereas DQ molecules as well as DR molecules stimulate equally auto MLR. 3) We also determined the clone size of MLR reactive CD4+ T cells by the limiting dilution analysis. Frequencies of allo DR, auto DQ, and allo DQ reactive CD4+ T cells was estimated to be almost equal, but frequency of auto DR reactive CD4+ T cells was estimated to be far low. These results suggest the relatively high occurrence of auto DQ reactive clones which contribute significantly to auto MLR. These auto DQ reactive clones may not be eliminated as efficiently as DR reactive clones, because of lower expression of DQ molecules than DR molecules on bone marrow derived cells.     

DQ β sequences in HLA-DR4 haplotypes

A cDNA clone encoding the entire mature DQ β chain was isolated and sequenced from the DR4-Dw14 homozygous cell line, LS40. The sequence was compared with published DQ β sequences from cells expressing DR4-DQw3, and found to be identical. The lack of DQ β sequence polymorphism within this serotype (to date, DQ β sequences have been derived from five cell lines comprising three Dw subtypes) adds to the data that suggest a recent evolutionary divergence of Dw subtypes within DR4-DQw3.     

High precursor frequency of human T cells reactive to HLA-DQ molecules expressed on mouse L cell transfectants.

In humans, the HLA-DR molecule is a major stimulatory molecule of allogeneic mixed lymphocyte reactions (MLR) and a major restriction molecule for the presentation of soluble antigens to the T cell. Little is known of the biological function of HLA-DQ. To examine the size of the repertoire of precursor T cells recognizing the autologous or allogeneic HLA-DQ molecule, the frequency of T cells reactive to HLA-DQ was estimated in comparison with T cells reactive to HLA-DR. We made use of a limiting dilution analysis and mouse L cells transfectants expressing the HLA-DR or -DQ molecule, as stimulators. Human T cells recovered from a primary MLR stimulated with allogeneic peripheral blood lymphocytes (PBL) proliferated in response to L cell transfectants expressing HLA class II genes shared by the stimulator cells in the primary MLR. This observation suggested that the HLA class II molecules on L cell transfectants shared to some extent epitopes for alloreactive T cells with those expressed on human PBL. The precursor frequencies of CD4+ T cells reactive to allogeneic or autologous DQ molecules were as high as those of T cells reactive to allogeneic DR molecules and were estimated to be 1/800-1/1800. The frequency of the T cells reactive to autologous DR molecules was low (1/7200-1/16,000). The biological significance of the high frequency of HLA-DQ-reactive precursor T cells is discussed.     

Distribution of class IIDQ antigens on normal and leukemic lymphoid cells

The distribution of DQ as well as DR antigens was examined on lymphoid and monocytic cells at different stages of differentiation. In the B cell series, both immature and differentiating (under Staphylococcus aureus or pokeweed mitogen stimulation) B cells often lacked DQ molecules; among surface IgM+ and IgD+ cells, both DQ and DR molecules were detected except on cells from 30% of the lymphoid malignancies studied. T cells expressed DQ molecules only after stimulation; a DQ-DR+ phenotype was observed in a large number of cells after allogeneic stimulation, in certain antigen-specific T cell lines as well as in T cell lymphomas, suggesting that class II antigens had a distinct pattern of regulation. In the monocytic lineage, DQ molecules were expressed by most lymph node monocytes and only a low percentage (20%) of circulating monocytes.     

Sequence variation in Japanese HLA-DRw8 specificity.

There are four DRw8 haplotypes with different DQ alleles in Japanese: DRw8-DQw6 (w1), DRw8-DQw4, DRw8-DQw8(w3), and DRw8-DQw7 (w3). We previously reported the nucleotide sequence of DRB1 gene of DRw8-DQw6(w1) and it was named DRB1*08032. The nucleotide sequences of the other DRw8 DRB1 alleles and their correspondence to internationally recognized DRw8 subspecificities were still unclear. We have cloned these DRB1 genes and determined the nucleotide sequences. The comparison of the sequences with the published sequences revealed that the differences were occurred at two amino acid positions, and these four haplotypes are classified in two groups: (a) DRw8-DQw6(w1) and DRw8-DQw7(w3), and (b) DRw8-DQw4 and DRw8-DQw8(w3). The DRB1 molecules of DRw8-DQw6(w1) and DRw8-DQw7(w3) have Ser57 and Ile67, and those of DRw8-DQw4 and DRw8-DQw8(w3) have Asp57 and Phe67. The former has the same sequence as that of DRB1*08032, and the latter is same as that of DRB1*0802. The classification corresponds to the serologic subtyping, which divides DRw8 into DR8.1 and DR8.2, reported in the 10th Japan HLA Workshop.     

Cytotoxic effector cells against HLA antigens in strong linkage disequilibrium: identification of a strong,new, CML determinant

Three sets of cytotoxic effector cells were generated against the A1, B8, DR3 haplotype using haptoidentical individuals in three different families. The three sets of effector cells generated against this haplotype showed excellent reproducibility testing, strong cytotoxicity against their specific targets, low autologous kill, and segregation with the sensitizing haplotype within the family. When tested against a panel of cells bearing all combinations the A1, B8. DR3 antigens, a hierarchy of contribution of the individual HLA antigens as CML target determinants was seen. A new strong target cell determinant was identified by cytotoxicity with one of the effector cells not explicable in terms of the A1, B8, DR3 antigens or known HLA cross-reactivity. A family study demonstrated that this determinant clearly segregates with HLA. The success of this approach in defining new CML determinants may result from the generation of effector cells across a single haplotype in strong linkage disequilibrium or from the presentation of CML determinants in the context of self.     

Differential expression of HLA class II antigens on human fetal and adult lymphocytes and macrophages

A panel of monoclonal antibodies to monomorphic determinants of the MHC class II subregion locus products: DP, DR and DQ, was used to investigate the expression of these antigens on early lymphocytes and macrophages from human fetal liver (13-20 weeks), placenta (16 weeks and term) and cord blood, in relation to the class II phenotype of cells from adult tonsil and peripheral blood. Fetal liver sections and cell suspensions showed differential expression of class II antigens. DP was expressed at a higher frequency (11.0% of nucleated cells) than DR on lymphoid cells and macrophages from fetal liver, and DQ was either absent or expressed on less than 0.3% of nucleated cells. Consistent with this finding, DP but not DR or DQ antigens were observed on vascular elements and macrophages in the villi of 16-week placenta. At term, all three subregion locus products were expressed. Adult tonsil and peripheral blood B lymphocytes expressed DP, DR and DQ antigens with similar frequency; however, DQ was expressed at a lower frequency than DP and DR on cord blood B lymphocytes. In contrast, 30-50% macrophages from cord blood and adult peripheral blood expressed DP and DR, but fewer (5% and 18%, respectively) expressed DQ. These data suggest that class II antigens are expressed in the sequence DP, DR, DQ on developing lymphocytes. A similar sequence is suggested for macrophages.     

A Human Melanoma Cell Line, Recognized by Both HLA Class I and Class II Restricted T Cells, is Capable of Initiating both Primary and Secondary Immune Responses

We have characterized a melanoma cell line, FM3, established from a metastasis of a 75 year old female patient (HLA–A2, HLA–DQ7) with malignant melanoma. This cell line expresses both HLA class I and class II antigens, as well as several important accessory molecules at high levels. FM3 cells were shown to function as a stimulator of both allogeneic as well as autologous mixed lymphocyte tumour cell culture (MLTC). From these autologous MLTC we were able to generate cytotoxic T cell clones indicating that FM3 is capable of processing and presenting endogenous antigens.
We have used this cell line in a model system to investigate whether these cells were able to initiate and support an immune response with specificity for selected peptide antigens. The FM3 cell line was capable of presenting a HLA–DQ7 restricted ras derived peptide (5–21, 13Gly–Asp) to a previously established T cell clone, RM70. The ability of FM3 to function as an antigen presenting cell (APC) was comparable to that of an autologous Epstein Barr virus (EBV) transformed B cell line. The CD4⁺ T cell clone RM70 showed a peptide–specific anti–proliferative effect on FM3 cells. This growth inhibition was not due to cytotoxicity as measured in a standard 4h chromium release assay. The FM3 cell line also presented a HLA–A2 restricted nonapeptide derived from the influenza matrix protein. M 1 (58–66) to a CD8⁺ T cell line specific for this peptide. This resulted in an effective killing of the melanoma cells.
Together, these data suggest that some melanomas may initiate an immune response by presenting their own specific antigens in an immunogenic context, and subsequently serve as targets for T cells of both the CD4⁺ and CD8⁺ phenotype.     

Human autoreactive (Th0) CD4(+) T-cell clones with cytolytic activity recognizing autologous activated T cells as the target

In attempt to obtain a clue to understanding possible physiological roles played by autoreactive T cells, autoreactive T-cell clones originally derived from an allogeneic mixed lymphocyte culture have been analyzed for their target spectrum, lytic function and cytokine profiles. Five CD4(+) T-cell clones established from allogeneic MLR, in which the stimulator cells shared certain class II MHC antigens with the responder, turned out to be reactive to autologous PBL. Among these, three clones were cytolytic against autologous B-cell line. These three cytolytic autoreactive clones were shown to be capable of specifically lysing autologous activated T cells expressing class II MHC molecules, raising possibility that such autoreactive clones might play a role in negatively regulating T cell responses. Cytolysis by an autoreactive clone 21C5 was inhibited completely by concanamycin A (CMA) known as a specific inhibitor of perforin, suggesting an involvement of the perforin/granzyme system. T-cell clones derived from the same MLC showed distinct correlation between their specificity and lymphokine profiles. Thus, the three cytolytic autoreactive clones belonged to Th0, whereas the two noncytolytic autoreactive clones belonged to Th2 and three alloreactive CD4(+) clones derived from the same culture were of Th1 type.     

Dw subtypes of serologically defined DR-DQ specificities restrict recognition of cytomegalovirus

We have investigated the relationship between serologically defined (Ia) and T lymphocyte-defined (LD/Dw) determinants in restricted recognition of cytomegalovirus (CMV) by human T lymphocytes. T lymphocytes isolated from CMV seropositive individuals expressing DQw3/DR4/Dw4 antigens were "sensitized" to CMV in vitro; CMV-specific blasts were isolated and tested for their ability to recognize CMV presented by cells expressing different DR4-associated Dw antigens (i.e., Dw4, Dw10, Dw13, Dw14, and Dw15). Similar studies were also performed using T lymphocytes from individuals expressing DQw1/DR2/Dw2 specificities and antigen presenting cells (APC) expressing the DR2-associated Dw/LD subtypes, Dw2, Dw12, and LD-MN2. CMV-specific T cell blasts were used as responding cells in order to reduce nonspecific background alloresponses which occur with allogeneic APC. In all cases it was found that the determinants involved in restricted recognition of CMV were subtypic to the DR-associated Ia specificities. To distinguish whether Dw specificities associated with DQ or with DR molecules, or both, were involved in these responses, we used anti-DR (L243) and an anti-DQwl (S3/4) monoclonal antibodies (MoAb) to block CMV-specific responses. Both MoAb significantly blocked responses, suggesting that determinants associated with both DR and DQ molecules are involved in restricted recognition of CMV by T cells.     

The proliferative immune response to autologous Epstein-Barr virus transformed lymphoblastoid cells. II. Studies with HLA class II loss variants demonstrate a role for gene products other than DR and DQ

The Epstein-Barr virus (EBV) transformed lymphoblastoid cell line (LCL-721) and some of its HLA loss mutant derivatives were used to study the immune specificity of the autologous proliferative T cell response to antigens expressed as a result of EBV infection. We have measured secondary and tertiary proliferative responses to well-characterized variants that lack expression of some or all known class II gene products (DR, DQ, and DP). These experiments prove that the region mapping between DR/DQ and glyoxalase I (GLO) of one haplotype controls at least one specific restriction element which is recognized in the autologous response to LCL-721. Furthermore, specific proliferative responses to variants lacking expression of all known class II gene products indicate the recognition of determinants other than DR, DQ, and DP.     

Humanized transgenic mice expressing HLA DR4-DQ3 haplotype: reconstitution of phenotype and HLA-restricted T-cell responses

Many autoimmune conditions have close genetic linkages to particular human histocompatibility leukocyte antigen (HLA) class II genes. With the aim of establishing a murine model of autoimmune disease, we have generated an HLA DR4-DQ3 haplotype transgenic (Tg) mouse that expresses a 440-kb yeast artificial chromosome harbouring DRA, DRB1*040101, DRB4*010301, DQA1*030101, DQB1*0302 and all the internal regulatory segments. This Tg mouse line was crossed to human CD4 (hCD4) Tg mice and endogenous class II knockout mice (I-A(o/o) and I-E(o/o)) lines to generate a DR4-DQ3.hCD4.IAE(o/o) Tg line. The Tg DR and DQ molecules are expressed on the physiological cell types in these animals, i.e. on most B cells (>85%), dendritic cells (DCs) and macrophages but not on T cells, with levels of expression comparable with those of human B cells (where DR > DQ expression). The DR4/DQ3 transgenes fully reconstituted the CD4 T-cell compartment, in both the thymus and the periphery, and the analysis of the T-cell receptor repertoire in the Tg mice confirmed that these class II molecules were able to mediate thymic selection of a broad range of Vbeta families. HLA DR4- and DQ3-restricted T-cell responses were elicited following immunization with known T-cell determinants presented by these molecules. Furthermore, the DR4-DQ3-restricted CD4(+) T cells conferred protective antibody-mediated immunity against an otherwise lethal infection with Salmonella enterica var. typhimurium. These new DR4-DQ3 Tg mice should prove to be valuable tools for dissecting the importance of this class II haplotype in autoimmune disorders like rheumatoid arthritis.     

A supertypic HLA class II determinant shared by DR1 and DRw9, and crossreactive with DR2, defined by human monoclonal antibody

A human monoclonal antibody Pez.2F5, produced by a lymphoblastoid cell line, has been established in vitro by Epstein-Barr virus (EBV) transformation of B lymphocytes isolated from the blood of a volunteer immunized with allogeneic peripheral blood leukocytes (PBLs). The antibody reacted with a new supertypic determinant expressed on all lymphoblastoid cell lines homozygous for HLA-DR1, -2, and -w9. The genetic linkage of the Pez.2F5 determinant to the HLA region was demonstrated by family segregation studies. Quantitative absorption studies indicated that DR2-positive cells required more Pez.2F5 antibody for lysis, and since their absorption capacity was significantly lower than that of DR1- or DRw9-positive cells, it is likely that the Pez.2F5 determinant of the DR2 haplotype is crossreactive but not identical with the determinant found on the latter haplotypes. In addition, on a test panel of HLA-typed B lymphocytes, Pez.2F5 showed perfect correlation with DR1 and DRw9, but reacted with only a fraction of DR2-positive cells. The Pez.2F5 determinant was found to be absent from resting T lymphocytes, but its expression could be identified on IL-2-dependent T-cell lines by cytotoxicity and flow cytofluorometric analysis. By sequential immunoprecipitation and SDS gel analysis of antigens of DR1 cells it was determined that the Pez.2F5 determinant is carried by HLA class II DR molecules. Thus, the Pez.2F5 is the first described human monoclonal antibody able to immunoprecipitate HLA class II-related molecules.     

HLA FIVE-LOCUS HAPLOTYPES IN FINNS

The extreme polymorphism of HLA genes makes them a powerful tool for distinguishing between different genetic populations. Five-locus HLA haplotypes of Finns (from Oulu, Northern Finland) are described here in order to characterize further the migration pathways of the population to Finland after the Ice Age. From random families, 364 haplotypes were obtained. The most frequent Finnish haplotype A3,Cw4,B35,DR1,DQ1 (7.7%) is a Caucasoid ancestral haplotype and is shared with Italians of Celtic and non-Celtic origin. The haplotype A1,Cw7,B8,DR3,DQ2, which occurs in 4.7% of Finns, is the most frequent haplotype in Caucasoids. The haplotypes A3,Cw7,B7,DR2,DQ1 (3.6%) and A2,Cw7,B7,DR2,DQ1 (2.5%) are shared with several Caucasoid populations and the latter also with Jamaican blacks. A2,Cw5,B44,DR5,DQ3 (0.8%) is shared with Italians of Celtic and non-Celtic origin, A2,Cw6,B13,DR7,DQ2 (1.1%) with Caucasoids in the USA and A9,Cw4,B35,DR1,DQ1 (0.8%) with Mongoloids. The haplotypes A2,CW3,B62,DR4,DQ3 (3.0%), A2,Cw2,B27,DR8,DQ4 (1.7%), A2,Cw3,B62,DR6,DQ1 (1.4%) and A2,Cw1,B27,DR4,DQ3 (1.4%) were also found to be among the most frequent in the Finnish population. The most frequent HLA haplotypes are consistent with the postulated ancient migration of populations from southern Scandinavia and Germany to Finland, the most frequent haplotype suggesting a common Celtic origin and one less frequent haplotype suggesting an influence from the east.