UNIQUE CD8(-CELL-RICH LYMPHOID AGGREGATES IN HUMAN UTERINE ENDOMETRIUM() T)

Using confocal scanning laser microscopy of viable tissue sections, we have demonstrated organized lymphoid aggregates (LA), that have a uni que structure, in the stratum basalis of uterine endometrium. These LA consist of a core of B cells surrounded by more numerous T cells and an outer halo of monocytes/macrophages. The T cells in the LA were alm ost exclusively CD8(+)CD4(-). These CD8(+) LA, in terms of both their T cell and B cell components, were either small or absent during the e arly proliferative stage of the menstrual cycle, significantly larger in size at mid-cycle and during the secretory phase, and absent in pos t-menopausal women, suggesting that their development is hormonally in fluenced. This new finding of a menstrual cycle-dependent, phenotypica lly unique, organized immune cell structure may lead to new insights i nto the mechanisms by which the endometrium accepts a semiallogeneic g raft while providing resistance to infectious organisms.