Adenoids provide a microenvironment for the generation of CD4(+), CD45RO(+), L-selectin(-), CXCR4(+), CCR5(+) T lymphocytes, a lymphocyte phenotype found in the middle ear effusion

Adenoidectomy in children with otitis media with effusion reduces inflammat ion in the middle ear by an unknown mechanism. Potentially, the adenoids of these children may serve as a site for the differentiation of lymphocytes, which after entering blood circulation eventually extravasate in the middl e ear mucosa and thereby contribute-to excessive inflammation. During lymph ocyte extravasation various adhesion molecules and chemokines play a crucia l role. To evaluate possible connections between the adenoids and middle ea r inflammation, the expression of the chemokine receptors CXCR4 and CCR5 an d the lymphocyte homing receptor L-selectin were analyzed in adenoidal and middle ear lymphocytes. It was found that most CD4(+) T lymphocytes in the middle ear effusion express the memory phenotype marker CD45RO and the chem okine receptors CXCR4 and CCR5, but are negative for the lymphocyte homing receptor L-selectin, This cell phenotype was rare in peripheral blood but w as found much more frequently in the adenoids, The results suggest that the adenoids provide a microenvironment for the generation for CD4(+), CD45RO( +), L-selectin(-), CXCR4(+) and CCR5(+) T lymphocytes, Further, these cells may include cells that have the capacity to home to the middle ear mucose. As the adenoidal CD4(+) memory phenotype CD45RO(+) T cells expressed the a ctivation antigen CD69 and included cells expressing the HIV co-receptors C XCR4 and CCR5 at a high level, they may be permissive for HIV infection.