Immunity in malaria: II. Heterophile and malarial antibodies in acute Plasmodium falciparum infection.

The sera of 55 Nigerian children (30 malarious and 25 healthy) were analysed for heterophile antibodies against normal sheep erythrocytes by the passive haemagglutination technique. Fluorescent antibodies to Plasmodium falciparum were quantified by the indirect immunofluorescence method while the three major immunoglobulins (IgG, IgA and IgM) were estimated by the radial immunodiffusion technique. An increasing age gradient was demonstrated in the heterophile antibody titres within the malarious and control groups, but there was no significant difference in the levels of immunoglobulins and malarial antibodies between the two groups. An indication of higher malarial antibody titre was only observed in the malarious group, particularly in late childhood. These results show an increasing level of heterophile antibodies with age. It is concluded that malarial antigens may play a contributory, but not a dominant role in the acquisition of heterophile antibodies. There is also a need to define the exact serum factors (antibody or non-antibody) which are associated with clinical immunity to malaria in Nigerian children.