Serological characterization of natural antihuman lymphocytotoxic antibodies in mammalian sera.

Abstract

A widespread occurrence of “natural” antihuman lymphocytotoxins in a number of mammalian and avian species has been observed by examining 483 sera at various dilutions. As targets, human lymphocytes from more than 80 healthy subjects were used in the complement-dependent cytotoxic test. All sera from rats, dogs, goats, cows, and ducks were cytotoxic to human lymphocytes. A decreasing proportion of sera from chickens (95%), sheep (93%), mice (67%), rabbits (36%), turkeys (9%), and guinea pigs (8%) were cytotoxic. Horse and pigeon sera were completely negative. Population and sibling studies showed that none of the 191 lymphocytotoxic normal mammalian sera and their dilutions correlated with any of the 25 HL-A specificities tested. However, patterns of reactivity in different sera could be classified into distinct categories. Cold lymphocytotoxins (15 C) were found in rat, goat, cow, and guinea pig sera. Some of the natural antibodies were also cytotoxic when human serum was the source of complement, or when sera were incubated at 56 C for 30 min before testing with lymphocytes. Absorption of normal mammalian sera with platelets from positive donors in many instances completely removed or greatly diminished the serum reactivity to donor lymphocytes. The origin of these antibodies is not known. It is conceivable that they result from stimulation by microbial antigens which in turn cross react with antigens on human lymphocytes.