Background: The ability of the host immune system to efficiently
clear Plasmodium falciparum parasites during a malaria infection
depends on the type of immune response mounted by the host. Study
design: In a cross-sectional study, we investigated the cellular-and
antibody responses in individuals with P. falciparum infection, in an
attempt to identify immunological signs indicative of the development
of natural immunity against malaria in Ibadan, Nigeria. Levels of
IL-10, IL-12(p70), IFN-γ, and IgM, IgG and IgG1-4 subclasses in
the serum of 36 symptomatic children with microscopically confirmed
malaria parasitaemia and 54 asymptomatic controls were analysed by
ELISA. Results: IFN-γ and IL-10 were significantly higher in the
symptomatic children (p=0.009, p=0.025 respectively) than in the
asymptomatic controls but no differences were seen for IL-12(p70).
Estimated higher ratios of IFN-γ/IL-10 and IFN-γ/IL-12 were
also observed in the symptomatic children while the asymptomatic
controls had higher IL-12/IL-10 ratio. The mean concentration levels of
anti-P. falciparum IgG1, IgG2, IgG3 antibodies were statistically
significantly higher in the individuals >5 years of age than <5
years while anti-P. falciparum IgG3 antibodies were notably low in
<5 years category. Children <5 years had higher IgM antibodies
than IgG and the expression of IgG subclasses increased with age.
Conclusion: Taken together, malaria infection is on a delicate balance
of pro- and anti-inflammatory cytokines. The higher levels of
IFN-γ seen in the symptomatic children (<6months) may be
instrumental in immune-protection against malaria by limiting parasite
replication. The observed variations in immunoglobulin subclass levels
were age-dependent and exposure-related