Effects of alloantibodies on lymphocyte proliferation in vitro

Inhibition of MLC responder and stimulator function with allo-antisera in rhesus monkeys

Ten antisera containing antibodies directed against specificities controlled by the Ia1 locus of rhesus monkeys were tested for their ability to inhibit the MLC reaction. In cultures with responding cells from the serum producer, all sera with anti-Ia1 activity depressed the stimulatory capacity of cells carrying the Ia1 antigen in question. In other responder/stimulator combinations, the stimulation-inhibition was Ia1-related for the majority of the antisera. These data provide further evidence for a possible identity (or close association on the cell membrane) between Ia1 and D locus determinants of rhesus monkeys. In addition, some sera showed an inhibitory effect also on responder cells (with cells from the serum producer as stimulators). There was no apparent relation of response inhibition to the Ia1 specificities detected by antisera.

Specificity of the inhibitory effect of a grand-multipara serum on MLC reactions and on responses to PHA, PWM and PPD

An MLC reaction inhibiting serum from a grand-multiparous woman (16 successful pregnancies) is described. The serum producer had the HLA antigen A3;Bw35/Aw19;B18;Dw2 and her husband the antigens A28;Bw35/Aw16;B18;Dw2, and they responded to each other in one-way MLC. The serum had the following characteristics: (1) it inhibited many but not all donors as stimulators in MLC; (2) it usually inhibited these same donors as responders in MLC, but clearly to a lesser degree and with a much lower titre; (3) the inhibition of the stimulating function followed HLA haplotypes in families, and seemed to have HLA-D associated specificity, inhibiting HLA-Dw3 and Dw6 homozygous but not HLA-Dw2 or Dw4 homozygous cells as stimulators; (4) it inhibited more strongly the PWM and PPD responses than the MLC responses of relevant cells; (5) the IgG fraction of the serum had characteristics similar to the non-fractionated serum; (6) the inhibitory effect on MLC reactions and PWM and PPD responses was not absorbable by specific red blood cells or platelets, but could be removed or diminished by specific lymphocytes; (7) the serum was not cytotoxic in the complement-dependent test against non-fractionated mononuclear cells or enriched B-lymphocytes. The findings and the possible biological and clinical significance of human Ia-like antibodies are discussed.

Thymus-derived rat lymphocyte receptor for cell surface antigens is a nonserologically defined product of the major histocompatibility gene complex

Recognition of cell surface antigens by nonsensitized thymus-derived rat lymphocytes is not affected by antisera against immunoglobulin, yet can be effectively blocked by treatment of the lymphocytes with alloantisera raised against lymphoid cells. However, allo antisera induced by nonlymphoid cells do not inhibit recognition. Adsorption of blocking antisera on immunoglobulin-Sepharose columns does not decrease their blocking activity. Absorption of blocking alloantisera with liver and kidney homogenates removes the cytotoxic alloantibodies, yet does not affect the capacity of the antisera to block recognition. Anti-H1-1 alloantisera block antigen recognition only of lymphocytes of strains that share the H1-1 locus. These results suggest that the constant part of the thymus-derived lymphocyte receptor for cell-surface antigens is a product of the rat major histocompatibility locus, which is not identical with the serologically defined antigens.