Reduced CD3/TCR complex expression leads to immunosuppression during Plasmodium falciparum malaria.

Inhibition of T cell function is an important pathological feature in malaria. We investigated which T cell population is reduced contributing to immunosuppression. We examined protein and RNA level of various cell receptors, specific for T cells in children having Plasmodium falciparum infection and compared those to healthy children of the same age. We observe reduced levels of cluster of differentiation (CD)3 and T cell receptor (TCR)alphabeta in both RNA and protein expression level. This reduced expression was associated with a collapsed membrane asymmetry as determined by enhanced annexinV binding. Also human leukocyte antigen (HLA)-A,B,C- and HLA-DR-positive cells increasingly bound annexinV. The enhanced binding of annexinV was paralleled by a reduced expression of transcription factors such as T cell transcription factor 7 and GATA binding protein 3, which are involved in the expression of T cell specific genes. Also the expression of the transcription factors major histocompatibility complex class II transactivator and regulatory factor X 5, which are part of the HLA transcription machinery, is reduced during infection. We show that two mechanisms may lead to a suppression of the immune system during malaria: cell damage and reduction of gene expression of the CD3/TCR complex.