SERUM IGA AND IGG SUBCLASSES DURING TREATMENT FOR ACUTE RESPIRATORY EXACERBATION IN CYSTIC-FIBROSIS - ANALYSIS OF PATIENTS COLONIZED WITH MUCOID OR NON-MUCOID STRAINS OF PSEUDOMONAS-AERUGINOSA

Patients with cystic fibrosis (CF) have a high prevalence of Pseudomon as aeruginosa infection which causes chronic infection of the mucosal surfaces of the lung. This results in recurrent immune stimulation and hypergammaglobulinemia. The present study examines the levels of circ ulating Ig classes, IgG and IgA subclasses in 13 adult patients with C F during acute pulmonary infection and post-exacerbation, Total serum IgG levels were raised in the patients during infection and post-treat ment when compared to the normal range (mean +/- SEM: 17.21 +/- 1.4 g/ l vs 16.45 +/- 1.5 g/l respectively; normal range 8 - 16 g/l). In cont rast, total IgM (2.6 +/- 0.26 vs 2.69 +/- 2.74 g/l; normal range 0.6 - 2.8 g/l) and IgA levels (2.5 +/- 0.52 vs 2.41 +/- 0.48 g/l; normal ra nge 0.5 - 4 g/l) remained unchanged when examined during all stages of the disease. Of the 13 patients studied, 69%, 39% and 31% had IgG, Ig M and IgA levels respectively raised above the normal range values. Th e mean levels of individual IgG subclasses examined in this group of p atients revealed values within the normal ranges, however IgG2 and IgG 3 were increased in 31% and 46% of patients. Individual IgG3 levels fe ll in 77% (10/13) and IgG4 in 62% (8/13) of the patients post-exacerba tion. With regard to IgA subclasses, significant reduction in the IgA1 levels were observed post treatment (3687 +/- 539 mg/l vs 2713 +/- 49 8 mg/l, p<0.01). In contrast, IgA2 levels were increased from 279 +/- 49 mg/l to 421 +/- 69 mg/l, although statistical significance was not reached. Upon antibiotic treatment for infection, the findings in this study show that IgA1 which is susceptible to bacterial proteases is r educed with a concommitant increase in the protease resistant IgA2 sub class. Moreover, patients colonised with non-mucoid strains of P. aero ginosa had higher total IgA levels due to the raised IgA1 subclass whe reas they had lower IgG levels due to low IgG2 and IgG4 subclasses.