Expression of complement receptor type 1 and type 2 in murine AIDS

Complement receptor type 1 (CR1and type 2 (CR2are expressed on the surface of B‑cells and follicular dendritic cells (FDCs in lymphoid follicles of mice. The importance of CR1 and CR2 in humoral immune response is well documented. Retrovirus‑induced immunodeficiency syndromemurine AIDS (MAIDSresults in abnormal humoral immune responsesdestruction of lymphoid structuresand loss of FDC functionsnamely trapping of antigens (Agsand their retention on the cell surface. We investigated the expression of CR1 and CR2 in the spleen and lymph nodes of mice withMAIDS. Flow cytometry and immunohistochemistry revealed the existence of a correlation between the decrease in the expression of CR1 and CR2 by B‑cells and the progression of the disease. Howeverexpression of CR1 and CR2 by FDCs was maintained in the later stage of the disease in which lymphoid follicles were destroyed and the ability of FDCs to trap and retain Ag was severely impaired or lost. MoreoverFDCs expressing CR1 and CR2 but not FDCs‑specific Ag (FDC‑M1 antigenproliferated in destroyed lymphoid structures. Although the ability of FDCs to trap and retain Ag in vivo was impairedFDCs trapped immune complexes supplemented with complements in cryostat sections. In additionFDCs proliferating in MAIDS displayed the same ultrastructural characteristic as normal FDCsand expressed CD23. We conclude that decreased CR1 and CR2 expression in B‑cells and continuous CR1 and CR2 expression in