Plasma immunoglobulin concentrations in an African (Gambian) community in relation to season, malaria and other infections and pregnancy.

IgG, IgA, IgM and IgD concentrations in plasma were measured at three surveys of a rural Gambian community made over 13 months. 3523 samples were analysed. The pattern of change with age of mean levels of each immunoglobulin class was similar at each survey, although IgM levels were highest in the survey made at the end of the wet season. Immunoglobulin levels in the same individual were found to be relatively stable in adults over the study period. Only minor correlations were found between the levels of different immunoglobulin classes in plasma from the same individual. Malarial parasitaemia was associated with increased mean IgG levels in age groups up to 20 years but with increased IgM levels only in the first 2 years of life. Plasma which contained precipitating antibodies to malarial antigens showed higher mean levels of IgG and IgM in most age groups. In association with splenomegaly mean IgG levels were increased throughout childhood while mean IgM levels were elevated only in the first 2 years. No consistent relationship between malaria and mean levels of IgA and IgD were noted. The only relationship found between haemoglobin concentration and immunoglobulin levels was a small negative correlation in respect of IgM. Clinical infection, other than malaria, was associated with increased mean levels of IgG and IgA in all age groups and of IgM in young children. Lower levels of IgG, IgA and IgM occurred in pregnancy; IgG levels seemed to fall progressively as pregnancy advanced. At certain ages mean levels of IgM and IgD were higher in females than males.