Glandular distribution of immunoglobulins, J chain, secretory component, and HLA-DR in the human endometrium throughout the menstrual cycle

Two-colour immunofluorescence was used to study components of the secretory immune system in the endometrium. Tissue sampling was performed in the follicular, ovulatory and luteal menstrual phase from women admitted for laparoscopic sterilization. The specimens were prepared for immunohistochemistry by a method that removes most extracellular immunoglobulin (Ig). The stroma contained only a few Ig-producing immunocytes, but was rich in HLA-DR positive cells. Most of the IgA- and IgM-producing immunocytes also expressed J chain, which is necessary for the generation of polymeric Ig (poly-Ig) with affinity for epithelial secretory component (SC or poly-Ig receptor). Throughout the menstrual cycle there was increasing accumulation of Ig within the endometrial glands, with preferential apical and intraluminal occurrence of IgA and IgM, usually along with J chain and SC. It is likely that some monomeric IgA (without J chain) and IgG enter the endometrial glands by passive diffusion from the stroma, but there is clearly an additional active external poly-Ig transport. Some of the glands stained for HLA-DR irrespective of the menstrual phase or degree of SC expression. Our findings suggest that active SC-mediated external transport of serum-derived (and to some extent locally produced) poly-Ig is enhanced in the luteal phase, and that SC and HLA class II molecules are differently regulated in the endometrial glands.