Immunity in malaria: depression of delayed hypersensitivity reaction in acute Plasmodium falciparum infection.

The effect of acute Plasmodium falciparum malaria infection on the cell-mediated immune response of 30 Nigerian children attending the General Out-patient (GOP) Clinic of the University College Hospital, Ibadan, Nigeria, was assessed in a controlled study. Delayed-type hypersensitivity skin reaction to five tuberculin units (5 TU) of purified protein derivative (PPD) was used as an indicator of cell-mediated immunity. The results showed marked depression of delayed hypersensitivity reaction to PPD in 27 (90%) of the malarious children, compared with four (16%) of the 25 control healthy subjects (P less than 0.0005). This depression was observed despite evidence of previous BCG vaccination in 38 (69.1%) of the 55 children in the study. The possible clinical significance of these observations in tropical paediatric practice, and the immunopathological implications, are discussed.