CIRCULATING IGA, IGC, AND IGM CLASS ANTIBODY AGAINST HAEMOPHILUS-PARAINFLUENZAE ANTIGENS IN PATIENTS WITH IGA NEPHROPATHY

We previously demonstrated a close relationship between the outer memb ranes of Haemophilus parainfluenzae (HP) antigens (OMHP) and IgA nephr ophathy (IgAN). Our objective was to clarify the relationship among IE A, IgG, and IgM class antibody against OMHP in the sera of 44 patients with IgAN and 62 patients with other glomerular diseases (OGD) by ELI SA. Patients with IgAN showed a significantly higher level of IgA anti bodies (P < 0.0005) and IgG antibodies (P < 0.001) against OMHP? than did patients with OGD. Positive correlations were observed between IgA and IgG antibodies, between IgA and IgM antibodies, and between IgG a nd IgM antibodies against OMHP in the sera of patients with IgAN. Immu noblotting showed that IgA, IgG, or IgM antibodies against OHMP in the sera of all patients with IgAN bound to the components of OMHP. Amino acid sequences of three components of OMHP recognized by the sera fro m patients with IgAN revealed homology with those reported for outer m embrane protein (OMP) P6 precursor, OMP P5, and P2 porin protein of H. influenzae. Results suggest that patients with IgAN have glomerular d eposits of OMP P6 precursor, OMP P5, or P2 porin protein of HP, and a specific increase in the production of IEA antibodies against OMHP via polyclonal activation against these, with switching of production fro m one isotype to another, e.g. from IgM to ISA.