Figure 7.

Platelet responses to bacteria can take place in the absence of functional Btk. (A) Characterization of bacteria-induced aggregation of platelets from X-linked agammaglobulinemia patients. PRP samples from two XLA patients were stimulated with crosslinked IV.3 mAb (IV.3-xl; 4 μg/ml IV.3 mAb followed by 30μg/ml F(ab’)₂ rabbit anti-mouse IgG), S. aureus Newman, E. coli RS218, 3 μg/ml CRP-xl, and 3 μM TRAP-6. Aggregation was measured by light transmission aggregometry. (B) PRP from XLA patients was incubated with 20 μg/ml IV.3 mAb (to inhibit FcγRIIA) or vehicle, before stimulation with either S. aureus Newman, E. coli RS218, 3 μg/ml CRP-xl or 3 μM TRAP-6. Aggregation was measured by light transmission aggregometry. Patient 1 (n=3, in different days) had a missense mutation in codon 28 affecting the Btk pleckstrin homology domain, which causes lack of Btk function. Patient 2 (n=1) had a mutation in exon 3 resulting in absence of Btk expression.