Expression of the C3d-binding protein (CR2) from Candida albicans during experimental candidiasis as measured by lymphoblastogenesis.

The complement C3d-binding protein (CR2) of Candida albicans has been purified by immunoaffinity chromatography, and its specificity has been characterized by immunoblotting with monoclonal antibodies to the C. albicans CR2 and the mammalian CR2. Recent studies with immunoelectron microscopy indicated that the CR2 was expressed during a systemic infection in a murine model of candidiasis. As a continuation of these observations, the immunogenicity of the C. albicans CR2 was investigated in a lymphoblastogenesis assay. Lymph node cells as well as splenic lymphocytes from mice infected subcutaneously with viable blastoconidia of C. albicans reacted to the C. albicans CR2 to a significantly greater extent than did lymphocytes from uninfected mice (P less than 0.01). The maximum stimulation of splenic lymphocytes by the purified receptor occurred at a concentration of 0.54 micrograms of protein per ml after 72 h of incubation of lymphocytes and receptor. Also, splenocytes from infected or CR2-immunized mice exhibited significantly reduced responses to the T-cell-dependent mitogen phytohemagglutinin (P less than 0.01). These data indicate that lymphocytes from infected mice respond to the C. albicans CR2 in a lymphoproliferation assay to a greater extent than do lymphocytes from uninfected mice, indicating that the CR2 is expressed in vivo.