CHARACTERIZATION OF B-CELL RESPONSES TO CHLAMYDIA-TRACHOMATIS ANTIGENS IN HUMANS WITH TRACHOMA

The circulating B-cell responses to Chlamydia trachomatis of 60 childr en and 34 adults in The Gambia were characterized in a cross-sectional study of different grades of trachoma, using the enzyme-linked immuno spot (ELISPOT) assay, Antibody-secreting cells (ASCs) specific to chla mydial major outer membrane protein (MOMP), heat shock protein 60, and whole elementary bodies were detected in children with no evidence of ocular disease, and the immunoglobulin (IgA) response was significant ly increased in those with follicular trachoma, In marked contrast, ch ildren with the most intense ocular inflammation paradoxically had an almost completely absent B-cell response of all isotypes and to all ch lamydial antigens, but with normal serum IgG and IgA responses, which was even lower than in the group with no ocular inflammation, Adults w ith or without evidence of trachomatous scarring had equivalent number s of circulating B cells, principally IgA, to all chlamydial antigens. Plasmablasts secreting antibodies to MOMP were present in the urine o f children in the absence of urogenital infection detectable by PCR, a nd relative numbers were 8 to 25 times higher than in blood, suggestin g site-specific homing within a common mucosal immune system, These re sults suggest that ELISPOT assay of ongoing B-cell responses detects s uppression of chlamydia-specific IgA ASCs during the proinflammatory r esponse to ocular chlamydial infection seen in intense trachoma, which may play a role in tissue damage leading to trachomatous scarring.