Defects in TNFRSF13C are the cause of immunodeficiency common variable type 4 (CVID4) , also called antibody deficiency due to BAFFR defect. CVID4 is a primary immunodeficiency characterized by antibody deficiency, hypogammaglobulinemia, recurrent bacterial infections and an inability to mount an antibody response to antigen. The defect results from a failure of B-cell differentiation and impaired secretion of immunoglobulins, the numbers of circulating B cells is usually in the normal range, but can be low. Primary antibodies are available purified, or with a selection of fluorescent CF Dyes and other labels. CF Dyes offer exceptional brightness and photostability. Note: Conjugates of blue fluorescent dyes like CF405S and CF405M are not recommended for detecting low abundance targets, because blue dyes have lower fluorescence and can give higher non-specific background than other dye colors.