Studies of congenitally immunologic mutant New Zealand mice. II. Absence of T cell progenitor populations and B cell defects of congenitally athymic (nude) New Zealand Black (NZB) mice

Congenitally athymic (nude) mice on an NZB, NZW, and BALB/c background were produced by repetitive selective backcrossing. F'₁₂ generation nude mice of these three strains were compared to their littermate nu/+ controls with respect to survival, histology, blood counts, splenic surface markers, response to mitogens, spontaneous plaque-forming cells, and appearance of naturally occurring thymocytotoxic antibodies (NTA). Under specific pathogen-free conditions, NZB nude mice survive less than 3 weeks, dying of a runting-like disease with infection by local normally noninvasive organisms. A contributing factor to this premature death is the relative absence of T cell progenitor populations in the NZB nude vs NZW nude or BALB/c nude groups. Furthermore, NZB nude mice have a significantly earlier appearance of NTA than nu/+ littermates and likewise appear to have heightened spontaneous polyclonal B cell responses against the haptens dansyl, nitroiodophenyl, trinitrophenyl, 2,4 dinitrophenyl, and sulfonate. It is suggested that NZB mice have several critical immunologic defects, including abnormalities of thymic epithelial cells, T cell differentiation pathways, and chronically polyclonal activated B cell populations. These defects interact to produce the clinical expression of autoimmunity.