Alteration of T-cell subsets in the lymph nodes from cats infected with feline immunodeficiency virus.

Alterations of T-cell subsets in the lymph nodes from FIV-infected cats in various clinical disease stages were examined histologically. In the early stage of infection (AP stage), follicular hyperplasia accompanied by expansion of the paracortical area was observed. Follicular involution and depletion with reduced paracortical area was observed in the ARC and AIDS stage nodes. The maximum section area of the entire popliteal lymph node was expanded significantly in the AP nodes. The paracortical area expanded in the AP nodes and decreased in the ARC and AIDS stage nodes. The cell density in the paracortical area in the AP nodes did not show a significant increase, while there was a significant reduction in the ARC and AIDS stage nodes. The lymph node CD4/CD8 ratio in the AP and ARC stages significantly decreased as compared with that of uninfected control cats, but conversion of the ratio was not seen. The estimated total numbers of CD4+ and CD8+ cells in the maximum section were increased in the AP stage but significantly decreased in the ARC and AIDS stages. Our study indicated that the lymphocyte depletion in the terminal ARC and AIDS stages of FIV infection was associated with both CD4+ cells and CD8+ cells. Findings obtained in this study might provide useful information for studying the pathophysiology of FIV infection.