Immunoglobulin A subclass distribution in serum from patients with the acquired immunodeficiency syndrome

Immunoglobulin levels are elevated in the acquired immune deficiency syndrome (AIDS) and one class, IgA, has been suggested as a marker of disease progression. IgA is composed of two subclasses, IgA1 and IgA2; circulating IgA1 is roughly 85% of the total in healthy individuals. We have attempted to determine if the subclass distribution in the serum of AIDS patients is similar to that of healthy subjects. IgA subclasses were measured by end-point radial immunodiffusion (RID). Sera from 27 AIDS patients and 27 controls who approximated the age and sex composition of the AIDS group were studied. Total IgA by RID, i.e., the sum of IgA1 and IgA2, correlated well with IgA determined by rate nephelometry (n = 51; r = 0.918; p less than 0.0001). Total IgA (IgAT), IgA1 and IgA2 were significantly elevated in the AIDS group (p less than 0.0001, p = 0.0001 and p = 0.033, respectively). However, the AIDS patients had a roughly equivalent percent IgA1 of total (87.2 +/- 7.6%) as the control group (85.0 +/- 6.1%). The subclass distribution is not altered in AIDS patients, and serum concentrations of IgA subclasses do not reflect possible alterations in secretory IgA which might be expected because of recurrent mucosal infections in these patients; nor is the subclass distribution altered due to clearance of predominantly IgA1-bearing immune complexes.