Tissue distribution of the human CD97 EGF-TM7 receptor

CD97 is a founding member of the EGF-TM7 family of class II seven-span tran smembrane (7-TM) receptors. CD97 has an extended extracellular region with several N-terminal epidermal growth factor (EGF)-like domains, which mediat e binding to CD55. Previous studies demonstrated the expression of CD97 on activated lymphocytes, monocytes, macrophages, granulocytes, and numerous h aematopoietic and nonhaematopoietic cell lines. Here, we determined the cel lular distribution of human CD97 in situ by immunohistochemistry M and immu nofluorescence (IF). Abundant expression of CD97 was detected on all types of macrophages and dendritic cells, except for microglia, Within the lympho id lineage, most T cells but only a few B cells express CD97. Germinal cent re B cells do not express the molecule. Except for smooth muscle cells, no staining was found on other cells outside the immune system. However, analy sis of a restricted set of epithelial tumors revealed CD97 expression on th e malignant cells in thyroid and gastrointestinal tract cancer.