Specific and non-specific immunological changes in epidemic polyarthritis patients

T-lymphocytes from epidemic polyarthritis patients exhibited a virus specific proliferative response when exposed to Ross River virus in vitro. The magnitude of this response was greater than that of lymphocytes from asymptomatic seropositive donors. The natural killer cell activity of peripheral blood mononuclear leucocytes from these patients was depressed early in disease but returned to normal levels as the severity of the symptoms decreased. Although no in vivo role can yet be assigned to natural killer cells in epidemic polyarthritis, changes in their activity appeared to be more closely associated with the presence or absence of disease symptoms than were levels of anti-viral antibody or the ability or T-lymphocytes from peripheral blood to proliferate on re-exposure to Ross River virus.