Codominant inheritance in immunogenetic (IR-gene) systems

HLA and disease

Many human diseases are associated with HLA class I, class II and class III antigens. It appears that the class III antigen disease associations can be explained by a direct defect operating at the level of either the class III gene or its gene product. The mechanism underlying class I and class II antigen disease associations is at present unknown. In this review we have considered thirty diseases which have been ranked according to their relative risk as defined by the frequency of a given HLA antigen in patient and control populations. The chronic inflammatory disorder, ankylosing spondylitis and its association with HLA B27 has been used as a model to study the HLA linked diseases. We have suggested that the disease may be caused by the Gram-negative microorganism Klebsiella which has antigenic similarity to HLA B27. It is proposed that some antibodies made against Klebsiella bind to HLA B27, thereby acting as autoantibodies leading to the pathological sequelae of chronic inflammatory arthritis. This is the crosstolerance hypothesis or molecular mimicry model and it has been compared to the receptor model. It is further suggested that the crosstolerance hypothesis can be utilised as a general theory to explain the association of other diseases with the class I and class II antigens, and offer a possible explanation for the polymorphism of HLA.

Immune suppression genes control the anti-F antigen response in F1 hybrids and recombinant inbred sets of mice

The immune response to the liver protein F antigen which, in the mouse, occurs in two allelic forms, is under sharp immunogenetic control in that only mice that possess the Ak molecule can respond to allo-F antigen. This response has been studied in a number of F1 hybrids between inbred strains and with recombinant inbred lines all of which express Ak, and which thus enable immune suppression effects to be detected. In the AKXL and AKXD sets the hybrids with CBA are responders if H-2k/H-2k, and usually nonresponders if H-2k/H-2b or H-2k/H-2d. Although this may be due to gene dosage effects, this cannot be the explanation for the low responsiveness of the H-2k/H-2b relative to the H-2k/H-2d mice found in CBA x BXD hybrids. For this, and other reasons, it seems likely that low responsiveness in any mouse possessing a responder Ak allele is due to suppression, and that this is mediated by the immune suppression effects of the non-H-2k haplotype. These H-2-mediated effects can be modified, both positively and negatively, by background genes. Thus, of the ten H-2k/H-2d members of the CBA x AKXD cross, seven are low responders and three are high responders. No other typed marker has the same strain distribution pattern at present. Major unresolved questions, therefore, concern the location and mechanism of action of the background genes and the mechanism of action of the H-2 immune suppression genes.

Two distinct high immune response phenotypes are both controlled by H-2 genes mapping K or I-A

Murine responses to immunization with 2, 4, 6-trinitrophenyl (TNP) conjugated to autogenous mouse serum albumin (MSA) in complete Freund's adjuvant (CFA) are controlled by a gene(s) in the K or I-A region of H-2 complex. High immune responses of both H-2d and H-2b mice have been mapped to this region of the major histocompatibility complex. No modifying effects were observed from genes to the right of I-A in either responder haplotype. High responsiveness controlled by Kb or I-Ab is inherited with complete or partial recessivity, depending on the route of immunization and the sex of the responder. However, high responsiveness controlled by Kd or I-Ad is inherited dominantly. This unusual pattern of inheritance of immune responsiveness to TNP-MSA is consistent with the genetic mapping to K or I-A. TNP-MSA-specific T-cell reactivity following immunization with TNP-MSA in vivo was examined utilizing a T-cell-dependent proliferation assay in vitro with cells obtained from high or low responder mice. Genetic mapping and mode of inheritance in this assay for antigen-specific T-cell reactivity corresponded with results obtained from a plaque-forming cell (PFC) assay measuring antibody production by B cells. Both the proliferative and PFC responses are probably under the same Ir gene control. Both gene dosage effects and Ir-gene-product interaction could influence the generation of specific immune responsiveness in F1 hybrids between high and low responders to TNP-MSA.

Three-receptor, clonal expansion model for selection of self-recognition in the thymus

The postulate is made that dual recognition by T lymphocytes is due to two types of receptor, one encoded by antibody genes and one by a distinct multigene family with simple rules for expression. This postulate leads to a model explaining ontogenic and evolutionary selection for self recognition, T lymphocyte effector function, the apparent high frequency of alloreactive T cells and immune response gene activity. The model is contrasted with previous explanations of self-recognition phenomena.

Immune response inversion after hyperimmunisation. Possible mechanism in the pathogenesis of HLA-linked diseases

The crosstolerance hypothesis suggests that animals sharing antigens with some microorganisms will produce low antibody levels in the early part and high levels in the latter part of an infection. Antibody responses have been measured in high responder B10.M and B10.D2 mice and low responder C3H and A.Thy-1.1, as well as F1 hybrids (B10.M X A.Thy-1.1) and (B10.M X C3H/He), after repeated immunisation with the antigen ferritin, involving altogether 483 mice. An inversion in the immune response was found to occur and similar delayed high antibody responses have been described in rheumatic fever. It is suggested a mechanism of immune inversion may operate in the pathogenesis of HLA and blood group-linked diseases.