Evidence for a compartmentalized B cell response as characterized by IgG epitope specificity in human ocular toxoplasmosis

Infectious agents in the eye induce both a local and a systemic Immoral imm une response. Previously, differences in Ag recognition were observed betwe en systemic and ocular derived IgG of patients with ocular toxoplasmosis. T his finding implied a nonrandom distribution of IgG-producing B cells in th e inflamed eye. In the present study, we compared the intraocular and syste mic B cell responses of patients with ocular toxoplasmosis to a single Toxo plasma gondii Ag. Two series of C-terminally deleted recombinant T. gondii GRA-2 proteins were constructed to delineate IgG B cell epitopes of paired ocular and serum samples. Differences in epitope region recognition between the ocular and systemic compartment were detected in 9 of 13 patients. The difference in distribution of GRA-2 epitopes between paired samples is ind icative of a local GRA-2 specific B cell population functionally different from the systemic GRA-2-specific B cell population. Our results suggest a s elective activation of a subset of B cells locally in nonlymphoid tissue.