Characterization of intraepithelial lymphocytes in human endometrium

Intraepithelial lymphocytes (IELs) were characterized and quantitated in normal non-pregnant endometrium and in early pregnancy decidua using H & E and phloxine tartrazine stains and a panel of monoclonal antibodies in an indirect immunoperoxidase technique. The relative numbers of granulated and non-granulated IELs varied according to menstrual cycle stage and in early pregnancy all IELs appeared to be granulated. There was a higher surface:gland ratio for IELs in proliferative endometrium compared with late secretory phase and early pregnancy endometrium. In proliferative endometrium most IELs were T cells, predominantly of the CD8 + subset. In first trimester decidua, higher numbers of CD56 + cells were observed, in keeping with the increased proportion of granulated IELs. IEL populations in human endometrium vary according to menstrual cycle stage and endometrial IELs appear to show phenotypic differences compared with IELs in the human gastrointestinal tract.