Specificity of Lymphocytotoxic Anti‐Human Antibodies in Normal Rabbit Sera

Abstract

Forty‐nine of 127 normal sera from New Zealand white rabbits were found to contain cytotoxic antibodies against human lymphocytes. Reactions with these sera did not correlate with those of known HL–A or ABO specificities. However, four distinct specificities were found in 18 sera. These antibodies are labile upon prolonged storage at −20°C and heating at 56°C for 30 min and have low avidity. Since rabbit serum is the most efficient source of complement in the cytotoxic reaction with human lymphocytes, the quantity as well as the specificity of these natural antibodies in rabbit serum have to be considered when selecting this reagent for the lymphocytotoxic test.

Rabbit Complement in the Lymphocytotoxicity Test

“…Rabbits' natural antibodies to human lymphocyte antigens are mainly IgM in nature, activate the classical pathway of the complement system (Ferrone et al 1974a) and are directed to a human polymorphic antigenic system which is distinct from other cell surface markers (Mittal et a! .…”

“…2) Density and spatial relationship of HLA antigens with lymphocyte antigens reacting with natural rabbit antibodies. Discordant reactions of normal rabbit sera with lymphocytes from HLA identical siblings have suggested that lymphocyte antigens segregate independently from HLA antigens (Mittal et al 1973), but no data are available on the spatial relationship between various HLA specificities on lymphocyte membranes and antigens that react with natural rabbit antibodies. Points 1 and 2 may explain why not all the sera defining a given HLA specificity give unexpected reactions with a panel of human peripheral lymphocytes.…”