Concentration of anti-pneumococcal capsular polysaccharide IgM, IgG and IgA specific antibodies in adult blood donors

OBJECTIVES Anti-pneumococcal capsular polysaccharide (PCP) IgM, IgG and IgA ELISAs have been developed to aid assessment of the adaptive immune system. The relationship between the concentrations of PCP IgM, IgG, and IgA was investigated. DESIGN AND METHODS The concentrations of PCP IgM, IgG, and IgA were measured in sera obtained from 231 adult blood donors. RESULTS Concentrations of each isotype were not normally distributed. The median concentration for PCP IgM was 54 U/mL (range 37-75 U/mL), IgG 40 mg/L (range 26-79 mg/L) and IgA 21 U/mL (range 13-44 U/mL). The median PCP IgM titres decreased with age and were significantly lower in patients aged 81-90 years compared to those aged 18-80 years. By contrast, there was a significantly higher median serum PCP IgG titre in the 61-90 years group compared to those aged 18-60 years and a significantly higher median serum PCP IgA titre in the 51-90 years group compared to those aged 18-50 years. The correlation between PCP IgG and IgA was more significant than between IgM and IgA and between IgM and IgG. Correlation of PCP IgA and IgM concentrations identified four phenotypes: high PCP IgM and IgA; high PCP IgM only; high PCP IgA only; and low PCP IgM and IgA. A significant number of individuals with a PCP IgG concentration >50 mg/L had low PCP IgA and IgM concentrations. CONCLUSION The additional measurement of PCP IgA and PCP IgM, alongside PCP IgG, in individuals investigated for a compromised immune system may provide a more detailed antibody profile.