The expression of secretory component (SC) by human glandular endometrial cells cultured in vitro was significantly increased by estradiol in the medium. Interferon-gamma and interleukin-4 stimulated the expression of SC only in the presence of estrogen. Tumor necrosis factor-alpha plus estrogen also caused a significant increase in the number of cells expressing SC. HLA class II antigen DR was detected on few glandular epithelial cells of human endometrium cultured in control medium, whereas interferon-gamma and interleukin-4, but not tumor necrosis factor-alpha, caused significant increases in the expression of DR. Estrogen in the culture medium did not significantly affect DR expression. The human endometrial adenocarcinoma cell lines, HEC and RL-95, expressed SC in approximately 50 and 20% of the cells. Also, approximately 20% of the RL-95 cells stained for DR antigen. Interferon-gamma did not influence the degree of expression of either surface marker of the two cell lines. Cells of both lines bound polymeric IgA and IgM but showed little to no binding of monomeric IgA, IgG, or an IgM previously shown not to bind SC. © 1993 Plenum Publishing Corporation.