Occurrence of IgG Subclass Antibodies to Ovalbumin, Avidin, and Pneumococcal Polysaccharide in Children

The serum levels of the four subclasses of IgG to three different antigens–ovalbumin (OVA), pneumococcal polysaccharide (PNC), and avidin–were determined by enzyme-linked immunosorbent assay in three age groups of healthy children: 1.2-2.5 years (group A, n = 20), 6-7 years (group B, n = 21) and 15-17 years (group C, n = 20). The anti-OVA response in all groups was dominated by IgG1, IgG2, and IgG4 antibodies which generally increased in levels from group A to group B, but then declined significantly in group C. In all age groups, the IgG2 and IgG4 as well as the IgG1 and IgG3 responses were correlated; an association was also observed between IgG1 and IgG2 in groups B and C, but not in group A. The anti-PNC response was restricted to the IgG2 and IgG4 subclasses; correlation between these subclasses was seen only in group B children. The more predominant IgG2 antibodies increased dramatically in concentration from group A to group B, and then less remarkably in group C. Occurrence of the IgG1 anti-PNC antibodies was different which resembled the anti-OVA response. Responses to avidin, a protein derived from the same source as OVA, were different from the anti-OVA responses. These were low and confined to the IgG1 and IgG2 subclasses only and mainly to the younger children. A small group (n = 8) of 6- to 7-year-old atopic children who had a history of asthma or eczema appeared to have responses similar to their healthy counterparts.