DEPRESSED CD4(-LYMPHOCYTE PROLIFERATIVE RESPONSE AND ENHANCED ANTIBODY-RESPONSE TO VIRAL-ANTIGEN IN CHRONIC LENTIVIRUS-INDUCED ARTHRITIS() T)

The proliferative response of peripheral blood mononuclear cells (PBMC ) stimulated with caprine arthritis-encephalitis virus (CAEV) surface glycoprotein (SU) was depressed 4- to 20-fold in Saanen goats with chr onic CAEV-induced arthritis compared with asymptomatic goats. Phytohem agglutinin-stimulated responses were not depressed. Complement depleti on of PBMC with anti-CD4 or anti-CD8 monoclonal antibodies identified CD4(+) T lymphocytes as the antigen-responsive cells in both high-resp onder asymptomatic goats and low-responder arthritic goats, Serum anti body titers to CAEV SU were 8- to 32-fold higher in goats with chronic arthritis. Increased anti-CAEV SU titers as early as 3 months after i nfection predicted the eventual development of clinical arthritis. Thu s, CAEV-induced arthritis is associated with chronic B cell activation resulting from dominant type 2 immune responses to viral antigen. The clinical outcome of CAEV infection may be determined by differential activation of type 1 or 2 T lymphocyte phenotypes at or near the time of initial exposure to CAEV.