We have studied the effects of prepro-vasoactive intestinal polypeptide-derived peptides on lectin-induced lymphocyte proliferation and natural killer cell (NK) activity in cells from murine spleen, mesenteric lymph nodes, Peyer's patches, thymus and peripheral blood mononuclear lymphocytes (PBL). These peptides (vasoactive intestinal peptide (VIP), peptide histidine methionine (PHM-27) and peptide histidine valine (PHV-42)) showed differential effects in their immune response in a dose- and tissue-dependent manner. All peptides significantly decreased DNA synthesis in spleen (range: 45-30%), lymph nodes (range: 30-0%), Peyer's patches (range: 30-4%) and PBL (range: 30-16%). In these tissues there was no significant difference in their potency. In the thymus, however, PHM-27 (range: 27-15%) was significantly more potent (p less than 0.001) in inhibiting DNA synthesis than either VIP (range: 6-0%) or PHV-42 (range: 20-8%). The modulatory effects on NK activity by these peptides also showed an inhibitory effect. The order of potency was: VIP (range: 40-27%), PHV-42 (range: 22-11%) and PHM-27 (range: 20-8%). The presence of VIP inhibitor [( D-p-chloro-Phe6,Leu17]-VIP) at 10(-8) M in both functional assays caused a significant antagonism of the effects of VIP but not PHM-27 or PHV-42. Our results suggest the existence on lymphocytes of different receptors for prepro-VIP-derived peptides, and that they may be considered as important immunoregulatory molecules. Their mechanism of interaction, however, is not clearly understood.

Animals↗

PubMedDate not supplied

Rejection of transplantable AKR leukaemia cells following MHC DNA-mediated cell transformation.

Major histocompatibility complex (MHC) class I molecules can function as specific target antigens in T-cell-mediated cytotoxity. In addition, T cells can kill target cells through non-MHC antigens, for example, virally infected cells, if the target and effector cells express the same MHC class I antigens. Consequently, quantitative and/or qualitative variations in the expression of the H-2/HLA antigens on the target cells could interfere with MHC-restricted immune reactions. We have reported that the AKR leukaemia cell line K36.16, a subline of K36 (ref. 3), on which the H-2Kk antigen cannot be detected, is resistant to T-cell lysis and grows very easily in AKR mice. Other AKR tumour cell lines, like 369, which have a relatively large amount of H-2Kk on their surface, are easily killed by T cells in vitro and require a much larger inoculum to grow in vivo. Monoclonal antibodies against H-2Kk, but not against H-2Dk, prevented the killing by T cells. This suggests that some tumour cells grow in vivo because tumour-associated antigen(s) cannot be recognized efficiently by the host's immune system, due to the absence of MHC molecules which would function as restriction elements for T-cell cytotoxicity. We have tested this hypothesis by introducing the H-2Kk gene into the H-2Kk-deficient AKR tumour cell line K36.16 and have now demonstrated directly the biological relevance of H-2Kk antigen expression in the regulation of the in vivo growth of this tumour cell line.

Animals↗

PubMedDate not supplied

New HLA DNA polymorphisms associated with autoimmune diseases.

Certain class II determinants of the human histocompatibility locus antigens (HLA) have been implicated in the aetiology of several autoimmune diseases, including rheumatoid arthritis (RA) and insulin-dependent diabetes mellitus (IDDM). HLA-Dw4 was the first HLA determinant found to be significantly increased in RA patients compared with controls, while Dw4 and Dw3 were found to be significantly increased in IDDM patients. When the HLA-DR system was defined, RA patients were found to have an increased frequency of DR4 and IDDM patients an increased incidence of both DR4 and DR3 compared with controls. As the HLA-Dw specificities are narrower than the serologically defined DR specificities, it was of specific interest to the present study that Dw4, Dw10, Dw13, Dw14, Dw15 and DKT2 are included in DR4. We describe here new restriction fragment length polymorphisms (RFLPs) and, together with the newly described serologically defined DQ specificity TA10, test their prevalence and associations in controls and diseased patients. We find that the newly characterized DNA bands are present at a much higher frequency in RA and IDDM patients than in controls. These findings may lead to a greater understanding of the pathogenesis of such diseases.

Arthritis, Rheumatoid↗

PubMedDate not supplied

MHC antigens and malignancy.

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Animals↗