Phenotypic analysis and proliferative responses of human endometrial granulated lymphocytes during the menstrual cycle

The in vivo function of the unusual population of CD56+ CD16- endometrial g ranulated lymphocytes (eGLs) in human endometrium is unknown; their increas ed numbers in the secretory phase of the menstrual cycle suggests that they may play a role in the immunobiology of nonpregnant endometrium. II? the p resent study, the phenotype and proliferative responses of eGLs at various phases of the menstrual cycle were compared with those in early pregnancy. Endometrial GLs were highly purified (> 98% CD56+) using immunomagnetic sep aration, and the expression of cell surface antigens was examined in smears using a double immunohistochemical labeling technique. Proliferative respo nses to mitogens and interleukin 2 (IL-2) were assessed in hanging drops in 60-well Terasaki plates. There was low to no expression of CD3, CD8, CD16, HML-1, L-selectin, and CD25 (IL-2 receptor alpha) on CD56+ cells isolated from nonpregnant and pregnant endometrium. The expression of CD2, CD49a, an d CD122 (IL-2 receptor beta, IL-2R beta), however, increased from the proli ferative to the late secretory phase of the menstrual cycle. In contrast, C D11a, CD69, and CD49d expression was high and did not vary with menstrual c ycle phase; CD49d levels were significantly reduced in early pregnancy. Unl ike early-pregnancy eGLs, none of the CD56+ eGL cultures throughout the men strual cycle displayed phytohaemagglutinin (PHA)-induced lymphoproliferatio n. In contrast, eGLs from nonpregnant endometrium in the presence of 5 or 1 00 U/ml IL-2 after 48- and 120-h incubation showed significant proliferativ e responses, as did eGL cultures from early pregnancy. A significantly redu ced number of proliferative phase eGL cultures proliferated in response to IL-2 compared to secretory phase and early-pregnancy eGL cultures. The IL-2 -induced proliferative responses of CD56+ eGLs were associated with increas ed IL-2R beta (CD122) expression. These findings demonstrate 1) differentia l eGL expression of CD2, CD49a, and CD122 during the menstrual cycle; 2) di fferential IL-2-induced eGL proliferative responses during the menstrual cy cle; and 3) differences between eGLs from nonpregnant and pregnant endometr ium in CD49d expression and their ability to respond to PHA.