Polypeptides immunologically related to band 3 are present in nucleated somatic cells.

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Abstract
Band 3, the major transmembrane polypeptide of erythrocytes, mediates the exchange of anions (chloride and bicarbonate) across the membrane. Band 3 was believed to be present on nucleated somatic cells as well as erythrocytes because the senescent cell antigen that is immunologically related to band 3 is present on lymphocytes, platelets, adult liver cells and embryonic kidney cells; and antibodies prepared against the senscent cell antigen isolated from leukocytes react with erythrocyte band 3. For this reason, human fibroblasts [foreskin, ATCC 153] lung cells, neutrophils, mononuclear leukocytes, [SW 2224] squamous epithelial (mouth) cells, [SW 1271] lung squamous epithelial carcinoma, mouse [HTZ] neuroblastoma cells and rat hepatocytes were examined for immunoreactive forms of band 3 by using monospecific antibodies to erythrocyte band 3. Polypeptides sharing common antigenic determinants with erythrocyte band 3 are present in nucleated somatic cells as determined by immunofluorescence, immunoelectron microscopy and immunoautoradiography. Peptide mapping revealed substantial sequence homology between erythrocyte band 3 and the band 3-like protein of leukocytes. Immunofluorescence studies indicate that the band 3-like proteins is nucleated cells participate in antibody-induced cell surface capping.