Abstract
The in situ distribution of C3 receptor-positive cells was analyzed by immunoperoxidase staining of normal and malignant lymphoid tissue with an anti-C3 receptor serum (AC3RS). AC3RS immunostaining coincided well with the pattern found previously with the erythrocyte-antibody-complement complex (EAC) adherence technique. This indicates that AC3RS is a new tool for the detection of C3 receptors in situ. In addition, evidence is presented that the different results obtained in molecular weight analyses of human C3 receptor molecules may be due to different preparation procedures. When human tonsillar lymphocyte membrane fractions were solubilized, and then radioiodinated, subunits with apparent molecular weights of 38,000 and 18,000 could be precipitated from these lysates with AC3RS. When whole cells were tritiated and then solubilized, only one component with an apparent molecular weight of 200,000 could be isolated with AC3RS.