SPECIFICITY OF THE INHIBITORY EFFECT OF A GRAND-MULTIPARA SERUM ON MLC REACTIONS AND ON RESPONSES TO PHA, PWM AND PPD

Abstract

An MLC reaction inhibiting serum from a grand‐multiparous woman (16 successful pregnancies) is described. The serum producer had the HLA antigens A3;Bw35/Aw19;B18;Dw2 and her husband the antigens A28;Bw35/Aw19;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 la‐like antibodies are discussed.