Aberrant Ae (E beta) Ia polypeptide chain in H-2g2 haplotype mice. Possible result of an intragenic recombination or mutation

Biochemical confirmation of recombination within the B-G subregion of the chicken major histocompatibility complex

Analysis of the B-G antigens of eight chicken major histocompatibility complex (B) system recombinant haplotypes by high resolution two-dimensional gel electrophoresis has provided evidence for the transfer of the complete B-G subregion in seven cases. In the eighth, a partial duplication within the B-G subregion appears to have occurred. In this recombinant, the entire array of polypeptides associated with one parental allele, B-G23, is expressed together with nearly the entire array of B-G polypeptides of the other parental haplotype, B2. This compound polypeptide pattern corroborates the serological evidence for a partial duplication within the B-G subregion and provides indirect evidence for the existence of multiple loci within B-G and for a means by which polymorphism may be introduced into the chicken major histocompatibility complex.

Alloreactivity of an OVA-specific T-cell clone. I. Stimulation by class II MHC and novel non-MHC B-cell determinants

A T-cell clone (Ly1-03) derived from BALB/cBy mice, though highly specific for OVA/Ad, reacted to allogeneic spleen cells of 6 of 12 H-2 haplotypes tested. The reactivity to each particular H-2 haplotype required the expression of a non-major histocompatibility complex (MHC) gene product present on the B cells of certain strains of mice. All the alloreactive responses were MHC restricted and were inhibited by class II-specific and L3T4-specific monoclonal antibodies. The non-MHC gene product, X, is a new lymphocyte-stimulating determinant that is not expressed in mice with the xid defect. We favor a model that proposes two independent sites (or receptors) for X and the class II molecule. Contrary to previous models for alloreactivity, the anti-MHC site is not directed to a polymorphic receptor for self-class II epitope on the foreign class II molecule, but rather to a conserved determinant present on both self- and allo-class II molecules. If there is only one antigen receptor on the T-cell clone Ly1-03, then anti-X receptor must bind to a cross-reactive determinant found on immunogenic OVA and the non-MHC coded gene product expressed on the cell surface membrane. We further postulate that class II plus "X" recognition may be a general rule for alloreactive as well as autoreactive responses. Thus, both allo-class II and allo-class I reactive T cells are similar in that both bind a non-MHC coded gene product prior to activation.

Molecular analysis of the hotspot of recombination in the murine major histocompatibility complex

Biological and serological assays have been used to define four subregions for the I region of the major histocompatibility complex (MHC) in the order I-A, I-B, I-J, and I-E. The I-J subregion presumably encodes the I-J polypeptide of the elusive T-cell suppressor factors. Restriction enzyme site polymorphisms and DNA sequence analyses of the I region from four recombinant mouse strains were used to localize the putative I-B and I-J subregions to a 1.0-kilobase (kb) region within the E beta gene. Sequencing this region from E beta clones derived from the two mouse strains: B10.A(3R), I-Jb and B10.A(5R), I-Jk initially used to define the I-J subregion revealed that these regions are identical, hence the distinct I-Jb and I-Jk molecules cannot be encoded by this DNA. In addition, the DNA sequence data also refute the earlier mapping of the I-B subregion. Analysis of the DNA sequences of three parental and four I region recombinants reveals that the recombinant events in three of the recombinant strains occurred within a 1-kb region of DNA, supporting the proposition that a hotspot for recombination exists in the I region. The only striking feature of this hotspot is a tetramer repeat (AGGC)n that shows 80 percent homology to the minisatellite sequence which may facilitate recombination in human chromosomes.

Methods of detecting mature human Ia-like antigen and their metabolic precursors

Ia antigens were shown to be present in the cell almost exclusively as mature alpha beta dimers which split into separate alpha and beta chains after boiling in SDS. In contrast metabolically labelling the cells with [35S]methionine resulted in only free alpha and beta chains being labelled. It is concluded that this widely used type of labelling, although useful for studying intermediate synthesis, should not be used for labelling mature cell surface molecules.

IR gene regulation of the response to trinitrophenyl-polysaccharides. Two independent genes are required for antibody production

The primary in vitro antibody response to TNP-Ficoll was found to be under H-2-restricted Ir gene control. Strains B10(H-2b), B10.A(H-2a), and B10.S(9R) (H-2t4) were consistently low responders while strains D2.GD(H-2g2), B10.GD(H-2g2), and B10.S(H-2s) were high responders. The in vitro TNP-Ficoll response in congenic recombinant and F1 hybrid mice demonstrated the requirement for complementation of two independent Ir genes. One Ir gene mapped in or to the left of the I-A subregion with high responder alleles being s or d. The second Ir gene mapped to the right of the I-E subregion and required b or s alleles for complementation. These results were further supported by the ability to block the TNP-Ficoll response by appropriate anti-Ia serum pretreatment of the antigen-presenting macrophages. When a structurally different polysaccharide antigen TNP-dextran was used, an identical pattern of restriction was observed.

Characterisation of Concanavalin A-binding glycoproteins from mouse splenic leukocytes by two-dimensional electrophoresis: preferential binding of incompletely glycosylated forms of H-2 antigen to the lectin

Concanavalin A (Con A)section-binding proteins from mouse spleen leukocytes were characterised by two-dimensional electrophoresis of material precipitated, by Con A plus anti-Con A, from lysates of biosynthetically-labelled cells. Although most cell surface (iodinatable) proteins are known to bind Con A, some of the major Con A-binding proteins detected by immunoprecipitation, after a four-hour biosynthetic labelling period, are not iodinatable and are probably intracellular. Thus the major biosynthetically labelled Con A-binding species are: (i) a non-iodinatable, high molecular weight glycoprotein (C-145); (ii) intracellular precursors of secretory immunoglobulins (IgM and, probably, IgA); (iii) immature (not fully-sialylated) forms of H-2 D and K antigens; and (iv) Ia antigens. In the case of the H-2 antigens, (and possibly of other cell surface proteins) the selection of immature forms by Con A is not due to lack of biosynthetic labelling of mature products, but to preferential binding of Con A to incompletely glycosylated molecules.

Identification of a second class I antigen controlled by the K end of the H-2 complex and its selective cellular expression

Immunoprecipitates obtained from [35S]methionine-labeled spleen cells by using monoclonal antibodies specific for H-2Kd and H-2Dd have been separated by two-dimensional polyacrylamide gel electrophoresis. Analysis of these gel patterns revealed the presence of an additional product of the K end of the H-2d complex, designated here as H-2K'. To determine whether H-2K' is a unique protein or a differentially glycosylated form of the previously characterized H-2Kd histocompatibility antigen, nonglycosylated molecules labeled in the presence of tunicamycin were examined. The results showed that both H-2K and H-2K' have distinct nonglycosylated polypeptide precursor forms. The approximate molecular weight differences between the fully glycosylated and nonglycosylated molecules also indicated the presence of three oligosaccharide side chains on H-2K', as is the case with H-2Kd, whereas H-2Dd has only two oligosaccharide units. The cellular expression of H-2K' was also investigated. Comparison of H-2 antigens immunoprecipitated from normal spleen cells and from thioglycollate-induced adherent peritoneal exudate cells cultured in the presence or absence of supernatant fluids from concanavalin A-stimulated spleen cells revealed that H-2K' was not expressed on the adherent peritoneal cells. This indicates that H-2K' is expressed in a tissue-specific manner, unlike the classical histocompatibility antigens H-2K and H-2D.

H-2 haplotypes, genes and antigens: second listing. II. The H-2 complex

In this second part of the Second Listing, we describe genes that constitute the H-2 complex proper. Here, we define the complex functionally as consisting of class I and class II loci (see Klein et al. 1983a). The H-2-associated complement loci and the Neu-1 locus have been described in the first part of the Second Listing (Klein et al. 1982), but for completeness we list them here again in some of the tables. We include into the H-2 complex the cluster of Qa and Tla loci, which we consider as class I loci (Klein et al. 1983). The genetic map of the definitely established loci appears in Figure 1 and is based on the recent results of molecular genetics studies (Steinmetz et al. 1982 a, b). For historical reasons we also describe loci (regions, subregions) that were once thought to be part of the H-2 complex but either they have since been withdrawn, or their actual existence is at present uncertain. We first list loci (regions, subregions) that have been designated by capital letters (we call it Madman's Alphabet because of the frivolity with which symbols have been introduced and then withdrawn again), and then other loci believed to be associated with the H-2 complex. As in the First Listing (Klein et al. 1978), the core of the review in the Second Listing constitutes the tables of H-2 haplotypes, antigens, and determinants.

A molecular map of the immune response region from the major histocompatibility complex of the mouse

A stretch of 200 kilobases (kb) of DNA from the I region of the mouse major histocompatibility complex has been cloned and characterized. It contains the genes for the biochemically defined class II proteins E alpha, E beta and A beta. DNA blot analyses suggest that the I region may contain only 6-8 class II genes. Correlation of our molecular map with the genetic map of the I region confines two of the five I subregions, I-J and I-B, to less than 3.4 kb of DNA at the 3' end of the E beta gene where a hotspot for recombination has been observed. Indeed, the I-A and I-E subregions may be contiguous. If so, the I-B and I-J subregions are not encoded in the I region between the I-A and I-E subregions.

Cross-blocking studies with monoclonal antibodies against I-A molecules of haplotypes b, d and k

For assessment of the distribution of allodeterminants on I-A molecules, binding inhibition studies were performed with monoclonal anti-I-A antibodies (mAb) in which pairs of labeled and unlabeled mAb were tested for cross-blocking on spleen cells of H-2 haplotypes b, d and k. The data suggest that allodeterminants are randomly distributed on the surface of the I-A molecule. Comparison of mAb with cross-reactivity for b, d or k haplotypes indicates that the allelic forms of determinants are located in analogous positions on different I-A antigens.

Membrane insertion and oligomeric assembly of HLA-DR histocompatibility antigens

HLA-DR histocompatibility antigens are assembled in the endoplasmic reticulum. This assembly has been studied in vitro and in vivo. Three polypeptides are involved in forming the oligomeric structure of HLA-DR antigens, DR alpha chains (molecular weight 35,000), DR beta chains (molecular weight 29,000) and DR gamma chains (molecular weight 33,000). They are cotranslationally inserted into the membrane of the endoplasmic reticulum, and all span the membrane. The size of the cytoplasmic portion of DR alpha and DR beta is about 500- 1000 daltons, whereas that of the DR gamma chain is about 3000 daltons. Oligomeric assembly of DR alpha, DR beta and DR gamma chains occurs shortly after their synthesis in the endoplasmic reticulum. DR gamma chains are synthesized in excess of DR alpha and DR beta chains, and hence in the endoplasmic reticulum they are found either in a complex with DR alpha and DR beta or in a free form. Free DR gamma chains remain in the endoplasmic reticulum, whereas DR gamma chains present in the oligomeric complex with DR alpha and DR beta undergo intracellular transport. Their molecular weight increases during transport, probably because of the addition of complex sugars in the Golgi complex. This is followed by the detachment of DR gamma chains from the oligomeric complex and the appearance of DR alpha and DR beta chains on the cell surface. Whether any DR gamma chains appear on the cell surface is uncertain.

Intragenic recombination in an E beta gene for a murine Ia antigen

The recombinant strain D2.GD was originally typed as I-Ad by serological methods. Indeed, the A alpha and A beta chains of the I-A antigens appear to exhibit normal behavior by the criteria of serology and two dimensional gel analysis. However, the E beta chain encoded by the I-A subregion of this strain, one of the two components of the plasma membrane located I-E antigens produced in D2.GD X A.TFR5)F1 animals, has been demonstrated to be the product of an intragenic recombinational event between E beta genes from the d and b haplotypes. Sequence analysis suggests that the amino-terminal portion of the Eg2 beta chain is derived from the d haplotype and, therefore, that the coding strand for this gene is oriented centromeric leads to telomeric (5' to 3' direction). Finally, these data combined with the data of Rose and Cullen (17) allow the ordering of the genes within the I-A subregion as (H-2K), A alpha, A beta, E beta ... (H-2D).

Genetic control of the immune response to haemoglobin. III. Variant A beta (bm12) but not Ae (D2.GD) Ia polypeptides alter immune responsiveness towards the alpha -subunit of human haemoglobin

Mice bearing the I-A subregion mutation bm12 were immunized and challenged with the alpha -subunit of human adult haemoglobin. Under conditions in which parental B6/Kh mice respond, B6.C-H-2bm12 mice are inhibited nearly 100% in their ability to respond to challenge to the alpha-chain of haemoglobin. D2.GD mice which express a variant Ae (E beta) polypeptide of the I-E subregion can respond as well as B10.D2 mice to both subunits (alpha- and beta-) of haemoglobin. These observations as well as other genetic mapping data confirm the I-A mapping of alpha -chain-specific Ir genes and extend the genetic fine mapping to the A beta gene within the I-A subregion or a combinatorial Ia determinant generated by an interaction of A alpha and A beta. In addition they implicate the Ia.8 specificity in determining immune responsiveness to alpha -chain determinants.

An H-2 haplotype possibly derived by crossing-over between (A alpha A beta) duplex and the E beta locus

The B10.STA62 strain carries the H-2w27 haplotype derived from a wild mouse captured in the vicinity of Ann Arbor, Michigan. Products of two class II loci composing this haplotype, A alpha and A beta, are serologically, biochemically (by tryptic peptide mapping), and functionally indistinguishable from products controlled by the Ab alpha and Ab beta genes of the B10.A(5R) strain. In contrast, the polypeptide chain controlled by the third class II locus, E beta, is different from that controlled by the Eb beta gene. This Ew27 beta chain lacks an antigenic determinant present on the Eb molecule and carries determinants lacking on the Eb molecule, the Eb beta and Ew27 beta peptide maps differ in at least six peptides, and cytotoxic T cells specific for the Eb beta chains do not react with B10.STA62 target cells. This great difference between the Eb beta and Ew27 beta chains suggests that the corresponding genes have not been derived from one another by a direct mutational conversion; instead, H-2w27 appears to be a recombinant haplotype derived by crossing-over between the A alpha A beta duplex and the E beta locus. This is the first recombinant discovered separating these class II loci.

Major histocompatibility complex restriction of soluble helper molecules in T cell responses to altered self

Evidence for major histocompatibility complex (MHC) restriction of soluble helper effects was observed in the generation of syngeneic killer T cells to trinitrophenyl-altered self. Ia-bearing T cells obscure the observation of such interactions, thus, must be removed to detect MHC restriction of nonspecific soluble helper factor supernates (HFS). Genetic mapping studies demonstrated that the strain producing HFS must be compatible in the H-21A region with the strain utilizing the helper molecules for optimal helper signals to be delivered.