Shared antigenic determinants between rabbit antihuman brain and rabbit antihuman thymocyte sera: Relationship to the lymphocytotoxic antibodies of systemic lupus erythematosus

Antibodies to human brain, liver, and choroid plexus were produced by immunization of rabbits with fresh autopsy material in Freund's complete adjuvant, and then were absorbed with human AB cells. Rabbit anti-human brain serum was cytotoxic for peripheral blood T cells using the two-stage microcytotoxicity assay. In the presence of complement, it prevented formation of E rosettes and reduced responsiveness to Con A, PHA-P, and allogeneic cells. In the absence of complement, it was strongly mitogenic, much like rabbit anti-human thymocyte sera. Similarly, rabbit anti-human-brain sera could be absorbed with human peripheral blood T cells, but not with B cells or liver. Rabbit anti-human-liver and choroid plexus sera did not exhibit such T-cell specificity. Lymphocytotoxic antibodies were also studied in the cerebrospinal fluid of 11 patients with systemic lupus erythematosus, and of 31 neurologic disease controls. There was no correlation in SLE with presence of CNS disease and either titer or target cell specificity of lymphocytotoxic antibodies. In contrast, patients with multiple sclerosis or meningitis, possessing CSF lymphocytotoxic antibodies, had specificities directed only against T cells, suggesting their origin as autoimmunization with inflamed brain.