Murine acquired immunodeficiency syndrome (MAIDS) is characterized by 
lymphoproliferation, polyclonal B cell activation resulting in the production of 
autoantibodies, and a progressive immunodeficiency. These are all hallmarks of 
some autoimmune diseases. Yaa is a Y-chromosome-linked gene that accelerates 
autoimmune diseases in some autoimmune-prone strains of mice. To further 
elucidate a possible relationship with autoimmunity, the effect of the Yaa gene 
on MAIDS was investigated. Analysis of phenotypic and functional disease 
parameters revealed that Yaa does not accelerate MAIDS disease. This is probably 
due to the generalized activation of most or all lymphoid cells in MAIDS, which 
cannot be enhanced by the Yaa gene. This result is in accordance with the 
selective enhancing effect of the Yaa gene on the immune response against self 
and foreign antigens in a specific genetic background. It suggests that the 
autoimmune response associated with MAIDS is a secondary phenomenon. 
Interestingly, even in wild-type C57BL/6 mice, autoantibody production may 
contribute overproportionally to the hypergammaglobulinemia associated with 
MAIDS.