Immunohistochemical distribution of CD9, heparin binding epidermal growth factor-like growth factor, and integrin alpha 3 beta 1 in normal human tissues

The tetra-membrane-spanning protein CD9 forms a complex with a membrane-anc hored heparin binding epidermal growth factor-like growth factor (HB-EGF) a nd integrin alpha3 beta1 in some human and monkey cell lines. We show here the immunohistochemical distribution of CD9, HB-EGF, and integrin alpha3 be ta1 in normal human tissues. Distribution of CD9, HB-EGF, acid integrin alp ha3 beta1 was similar in various tissues, including transitional epithelium , squamous epithelium, thyroid follicular epithelium, adrenal cortex, testi s, smooth muscle, and stromal fibrous tissue. However, distribution of the three proteins did not coincide in some tissues, such as lung, liver, kidne y, gastric and intestinal epithelium, pancreas, salivary gland, and ovary. In striated muscle, including cardiac muscle, CD9 was present not in the mu scle cells themselves but in the endomysium and perimysium, whereas HB-EGF was distributed in the muscle cells themselves. CD9 was distributed in the myelin, but HB-EGF was found in the axon of the peripheral and central nerv ous systems. Coincident distribution of integrin alpha3 beta1 with others w as not observed in muscles and neural tissues. In conclusion, there is a po ssibility of complex formation and functional cooperation of CD9 with HB-EG F and/or integrin alpha3 beta1 in several tissues.