Methods: The B cells of three patients with recurrent infections and decreased antibody responses to polysaccharide vaccines were studied for response to specific B cell stimuli. Peripheral blood mononuclear cells (PBMC) were separated using density gradient centrifugation. Mature B cells (CD20+) excluding CD27+ (memory) and CD10+ (immature) cells were identified by flow cytometry. PBMCs were stimulated with various concentrations of F(ab’)2 anti-human IgG and IgM to initiate B cell antigen receptor (BCR) stimulation and with Imidazoquinoline to stimulate toll like receptors 7 & 8 (TLR 7/8). Mature B cell responses to these stimuli were assessed by flow cytometric analysis of the expression of the B cell activation marker CD86, and compared to stimulated cells from controls.
Results: Compared to controls, B cells of patients with impaired polysaccharide-specific antibody responses showed markedly lower CD86 expression at all concentrations of anti-BCR stimulation. In two patients, the CD86 expression following exposure to Imidazoquinoline was considerably lower compared to normal subjects.
Conclusions: Three patients unresponsive to polysaccharide antigens showed evidence of diminished activation in response to BCR stimulation. Two patients were also refractory to activation via TLR 7/8 pathways. It is plausible that these impaired activation pathways are responsible for the failure of these patients to respond to polysaccharide vaccines, but the defect may be heterogeneous.