P. Démant

Relationships between private and public H-2 specificities on the cell surface

Differential redistribution was used to investigate relationships between private specificity H-2.4 and public specificity H-2.28, in the product of aD region allele of theH-2 complex. Monospecific anti-H-2 antisera and fluorochrome conjugated antimouse Ig antibodies were used to induce redistribution of H-2 antigens on the surface of peripheral T lymphocytes fromH-2a andH-2d mice. Results showed that redistribution of specificity H-2.4 into patches and caps did not induce concomittant redistribution of specificity H-2.28, which remain diffusely scattered on the cell surface outside the caps of H-2.4. Redistribution of H-2.28 induced redistribution of H-2.4, which was no longer detectable outside the caps of H-2.28. These data indicate that (a) at least some of the H-2.28 sites are expressed on polypeptide chains independent from those carrying H-2.4 and (b) other H-2.28 sites may be linked to molecules carrying H-2.4. Since, onH-2a cells, both specificities are products of the D region of theH-2 gene complex, our results suggest that there are at least two genes in theD region.

SEPARATE AND POLYMORPHIC LOCI CONTROLLING TWO TYPES OF POLYPEPTIDE CHAINS BEARING THE H‐2 PRIVATE AND PUBLIC SPECIFICITIES

Serological and genetic analyses of H‐2 antigens indicate that each K or D region allele controls two highly polymorphic antigenic sites, the alpha site corresponding to the private specificity and the gamma site corresponding to the long public specificities. Studies of cell surface distribution and biochemical characteristics of the alpha type specificity H‐2.4 and gamma type specificity H‐2.28 in the product of a D region allele, Dd, demonstrate that these specificities are carried on two different polypeptide chains. Accordingly, two distinct and polymorphic genes are postulated to code for the product controlled by the D region of H‐2.

Topographical relationships among H-2 specificities controlled by theD region

In the present work, we used the differential redistribution method to study the molecular expression of several H-2 specificities controlled by theD region of theH-2a haplotype. We observed that: capping of the private specificity H-2.4 induced capping of the public specificities H-2.3, H-2.35, and H-2.36, and vice versa; capping of any one of these specificities did not induce capping of the public specificity H-2.28, controlled by the same region. By contrast, capping of the H-2.28 specificity induced capping of these specificities; redistribution of H-2K and H-2D private specificities or redistribution of H-2D private specificity and Ia specificities did not induce capping of the H-2.28 specificity. These data indicate that a part of a molecule carrying the H-2.28 specificity is linked to a molecule carrying H-2.4, H-2.3, H-2.35, and H-2.36 specificities and that a part of a polypeptide chain bearing the H-2.28 specificity is independent from that bearing other specificities controlled either by theD region (i.e., H-2.4, H-2.3, H-2.35, and H-2.36) or by theK andI regions. These results further strengthened the hypothesis of the existence of at least two genes controlling theD-region H-2 antigenic specificities.

THE GENETIC BASIS OF THE GENERATION OF EFFECTOR CAPACITY FOR CELL MEDIATED LYMPHOLYSIS IN MICE

The cell mediated lympholysis (CML) test is normally carried out in 2 steps–first, the lymphoid cells are allowed to interact in mixed allo‐culture (MLC) and secondly, they are reacted against chromium labelled phytohaemagglutinin transformed lymphoblast cells, carrying the appropriate target allo‐determinants. The genetic control of target structures has already been localized to the H‐2D and H‐2K regions of the H‐2 gene complex, but the genetic basis of the generation of effector capacity is not understood and is the subject of this report; the suggestion that there is a separate genetic basis came from the observation that H‐2D and/or H‐2K region incompatibility alone was insufficient for CML to occur and that incompatibility at the Ir‐Ss‐Slp regions of the H‐2 complex was also required. In the Ir region also reside the genetic control for the strong lymphocyte activating determinants (LAD) of the H‐2 gene complex and it was thought possible that they might also be responsible for activating the effector cells for CML.

I region associated histoincompatibility with absence of accelerated rejection of second set skin grafts detected in tests with a new haplotype, h-2dx.

H‐2 typing of two inbred mouse strains, GRS I/A and LIS/A, revealed that they both carry the same, previously unknown haplotype, designated H‐2dx. The H‐2dx haplotype has the K region allele identical or very similar to that of H‐2d, however it differs from H‐2d at the I region genes and has none of the D region alleles previously described in inbred mouse strains.

THE GENETIC BASIS OF ANTIGENIC STRENGTH IN HEART AND SKIN ALLOGRAFTING

Thirty‐one combinations of congenic and recombinant mouse strains were tested for heart and skin allograft survival times with and without ALS and the results compared with those obtained for MLR and CML. Although the genes for Lads, Ir and Ia specificities are all in the K end, on the average no greater strength of K end incompatibilities than D end were found. Some of the shortest survivals were D region only incompatible.

Defective MLR capacitation in the human: Low xenogeneic MLR capacity associated with HLA antigens AW25 B18, and DW2

In tests with 72 human donors, the outcome of the xenogeneic human-mouse MLR was influenced more by the general capacity of the human responder cells to react than by the MHS genotype of the mouse stimulating cells. While the response of the human lymphocytes of the same donor to the lymphocytes of six congenic mouse strains with differentH-2 haplotypes was generally rather similar, there were pronounced differences among individual human donors in the reactivity in these tests. These differences correlated with HLA, since the low reactivity was associated with the presence of the antigens HLA-AW25, HLA-B18, and HLA-DW2. The effect of the presence of antigens AW25, B18 was much more pronounced in males than in females. The low capacity to react in xenogeneic MLR in individuals with antigens HLA-AW25 and HLA-B18 may be the result of the general immune insufficiency associated with these antigens, which also includes C2 defficiency and association with immunopathological diorders.

Immunogenetic aspects of antigenic strength.

It is well known that the major histocompatibility system (MHS) has unique properties pertaining to antigenic strength (Démant, 1973). In the 1973 and 1975 Workshops we investigated alloimmune interactions to try to find out which MHS genes are involved and how they confer antigenic strength. We found that in several models there are special antigenic strength conferring and/or controlling genes, that there are probably several such genes unique for each model, situated throughout the mouse MHS (H‐2 complex). For example, the cell mediated lympholysis (CML) controlling genes, the Effector Cell Stimulating (ECS) genes, conferring strength against K and D region antigens are in the I region but separate from the I‐A Lad genes (Festenstein et al., 1974) while the allograft controlling genes, for various rejection models, are in the D region as well as the I region (Festenstein et al., 1975). This is an attempt to bring together the data from these various models to formulate a functional concept of antigenic strength, in relation to its genetic basis.

THE ROLE OF H-2 REGION INCOMPATIBILITIES IN GRAFT-VERSUS-HOST REACTIONS RAISED BY THYMUS CELLS

Graft‐versus‐host reaction, after injection of parental thymus cells into F1 hybrid recipients, was measured by popliteal lymph node assay in combinations of congenic strains which involve incompatibilities at various regions of the H‐2 gene complex. The results indicate that incompatibility at genes in the I‐A, I‐B regions or their vicinity results in the strongest graft‐versus‐host reaction. Incompatibility at genes associated with the I‐E region also was effective, while no graft‐versus‐host reaction was seen in combinations with I‐C, S, and D region incompatibility.

WORKSHOP SUMMARY ON GENETIC DETERMINANTS AND MECHANISMS OF CELL-MEDIATED IMMUNE REACTIONS—INCLUDING NEW METHODS OF DETECTION OF CELL MEMBRANE ANTIGENS AND THE BIOLOGICAL IMPLICATIONS THEREOF

It is now well established that the various parts of the H-2 gene complex differ from each other in their capacity to stimulate different types of alloimmune reactions (Dimant, 1973; Shreffler & David, 1975 ; this paper). This heterogeneity includes histocompatibility characteristics of individual regions, mixed lymphocyte reaction, graft-versus-host reaction, target structures for CML, and generation of effector capacity for CML. In the previous workshop (Festenstein & DCmant, 1973) we have analysed the role of different regions of H-2 in alloimmune reactions in several assay systems. The main points which emerged from this study were: