The binding of phosphorylcholine-carrying antigens to the anti-phosphorylcholine monoclonal antibody TEPC 15. A fluorescence spectroscopic study

The role of phosphorylcholine-specific immune responses in the tonsils and peripheral blood on IgA nephropathy

BACKGROUND

Tonsillectomy combined with steroid pulse therapy was reported to be effective for patients with IgA nephropathy. However, the mechanisms of the effect of tonsillectomy on IgA nephropathy are unknown.

AIM

The aim of this study was to investigate the involvement of the phosphorylcholine (PC)-specific immune response in the tonsils and peripheral blood of patients with IgA nephropathy.

MATERIAL AND METHODS

Tonsillar lymphocytes were isolated and the number of PC-specific immunoglobulin-producing cells was measured. Additionally, serum PC-specific immunoglobulin levels were quantified and compared with laboratory findings.

RESULTS

The number of PC-specific IgA-producing cells was increased in the tonsils of patients with IgA nephropathy. The value was significantly elevated in the group with a higher risk of initiating dialysis. In contrast, PC-specific IgM levels in the serum were significantly elevated in the group with a lower risk of initiating dialysis.

CONCLUSIONS AND SIGNIFICANCE

PC-specific immune responses in the tonsils and peripheral blood may be related to the pathological mechanism and progression of IgA nephropathy.

Microbial modulation of host immunity with the small molecule phosphorylcholine

All microorganisms dependent on persistence in a host for survival rely on either hiding from or modulating host responses to infection. The small molecule phosphorylcholine, or choline phosphate (ChoP), is used for both of these purposes by a wide array of bacterial and parasitic microbes. While the mechanisms underlying ChoP acquisition and expression are diverse, a unifying theme is the use of ChoP to reduce the immune response to infection, creating an advantage for ChoP-expressing microorganisms. In this minireview, we discuss several benefits of ChoP expression during infection as well as how the immune system fights back against ChoP-expressing pathogens.

Site-directed mutagenesis study of the antibody 2D7 which catalyzes a reaction for insertion of Cu2+ into mesoporphyrin

Monoclonal antibody 2D7 generated against a transition-state analog N-methyl mesoporphyrin catalyzes a reaction for insertion of a cupric ion into mesoporphyrin. To investigate amino acid residues responsible for the catalytic activity, site-directed mutagenesis of the amino acid residues in the third complementarity determining region of the heavy chain (CDRH3) was performed on the antigen-binding fragment (Fab) of the antibody. Recombinant Fab mutants, in which Arg95 is replaced with Ala (R95A), Asp96 with Asn (D96N) and Met97 with Gly (M97G), were examined in terms of the catalytic efficiency of the reaction (k/K(S)) and the dissociation constant for N-methyl mesoporphyrin binding (K(d)) and these values were compared with those of the wild type. The k/K(S) values of the R95A and D96N mutants were 0.96% and 1.0% of that of the wild type, respectively, whereas the M97G mutant had no detectable catalytic activity. The K(d) values of the R95A and D96N mutants were 165 and 69 times that of the wild type, respectively, while that of the M97G mutant was similar to that of the wild type. The relationship between the k/K(S) and 1/K(d) values in the wild type and the R95A and D96N mutants suggests that Arg95 and Asp96 are responsible for stabilizing the transition-state in the catalytic reaction. The results of the M97G mutant allow us to propose that Met97 plays an important role in the catalytic activity probably due to a subtle and specific conformation of the antibody.