According to the results shown in Table 2, the highest reactivity with specific serum IgA was observed when a linear peptide conjugated with BSA was used as an antigen in the ELISA test (mean for sera of healthy children: 0.7659 ± 0.0319, for sera of children with PID: 0.3693 ± 0.0236, for sera of blood donors: 0.9437 ± 0.0230). Here, CD79A is linked to pelvic inflammatory disease.