Fig. (2) (a). Western blot analysis of IgA1 protease recombinant protein. M: protein marker, 1: the IgA1 protease recombinant protein with ~28KDa MW. (b). Antibody responses in three age groups (A: <2 years, B: 2-40 years, C: > 40 years). The axis X shows titers10, 20, 40 and 160 and axis Y are serum samples’ ODs.