IMMUNOLOGICAL PROPERTIES OF HETEROZYGOUS NU + MICE - CHANGES IN ANTIBODY-RESPONSE AND INDUCIBILITY OF TOLERANCE TO PROTEIN ANTIGENS/

Heterozygous nu/+ mice are not fully identical in their immunological properties with the mice of wild +/+ genotype. A colony of nu/nu, nu/ and +/+ mice from the same breeding nucleus was established and their immune reactivity to human serum albumin, inducibility of adult immun e tolerance to hen egg lysozyme (HEL), sensitivity of their lymphoid c ells to stimulation by mitogens and ratio of CD3, CD4 and CD8 positive cell populations was studied. Both the numbers of antibody-forming ce lls in regional lymph nodes and the antibody titres in sera of nu/+ mi ce were highly variable, between undetectable values of nu/nu and high values of +/+ homozygotes. Intravenous pretreatment with soluble HEL, leading in +/+ mice to a deep hyporeactivity to subsequent immunizati on with the same antigen, did not decrease the response of nu/+ mice s ignificantly. These results indicate that the immunological alteration of nu/+ mice is not only quantitative and that T cell subpopulations might be differentially modified by the presence of nu allele. The fin ding of decreased CD4:CD8 ratio in nu/+ mice also supports this idea.