To evaluate the possible role of streptococcal cell wall antigens in the development of psoriatic arthritis.
IgM, IgA and IgG class serum antibodies against peptidoglycan-polysaccharide (PG-PS) and peptidoglycan (PG), both from group A streptococcus, were measured in patients with psoriatic arthritis (PA), non-arthritic psoriasis (NAP), rheumatoid arthritis (RA) and in healthy controls, using ELISA.
Both groups of psoriatic patients had elevated IgA levels specific to streptococcal PG-PS. No association with the severity of the skin disease or with the different subsets of PA was detected. Higher concentrations of IgG against the two streptococcal preparations was observed in PA than in RA. Analysis of antibody levels in patients with recent onset arthritis showed lower concentrations of IgM antibodies against streptococcal as well as control antigens in early than in late PA, whereas an overall increase of specific IgA and IgG antibodies was observed in early RA.
The results suggest chronic mucosal stimulation of lymphocytes by long-lived streptococcal antigens in patients with psoriasis, without any difference observed between PA and NAP. The differences between recent onset versus established PA and RA could reflect a distinct immunopathology in the two arthritides.