Serum IgG Subclasses Levels In Paediatric Patients With Pneumonia

Abstract

Bacterial pneumonia is the commonest cause of morbidity and mortality in Zimbabwe.1 The children most at risk are those infected with HIV 2-4 We reported, in a recent study 2 that the great majority of children admitted to hospital with pneumonia have hypergammaglobulinaemia in immunoglobulins A (IgA), G (IgG) and M (IgM) IgG was the most raised immunoglobulin class with concentrations of up to 10 times that of normal age-matched reference ranges. The report was in agreement with other studies done previously 3,5 More recent studies 6,7 have shown that the concentrations of total IgGl and IgG3, in various mucosal fluids, are increased in HIV-infected individuals while those of IgG2' and IgG4 are decreased. Furthermore, the concentrations of specific IgGl and IgG3 antibodies to HIV virus are correspondingly increased in the same HIV-infected subjects while specific IgG2 and IgG4 antibodies were reduced. It is now established that IgG2 type antibodies are the most effective against encapsulated bacteria such as Streptococcus pneumonia, particularly in young children's It would appear that children with low IgG2 levels would have correspondingly low levels of IgG2-type antibodies and therefore a deficient humoral immune response to encapsulated bacteria. Such a deficient immune response , would be further compromised by HIV infection. The main objective of this study was to investigate the relationship between levels of IgG subclasses and the occurrence of pneumoilia in children aged one month to six years with or without evidence of HIV infection.