Peripheral blood lymphocyte subsets in infants with diarrhea with and without Giardia lamblia infection.

The aim of the present study was to define the cellular immune response during gastrointestinal Giardia lamblia infection in young children. The level of lymphocyte subsets was determined in the peripheral blood of infants with G. lamblia-associated diarrhea or acute gastroenteritis and from control infants without diarrhea. The proportion of peripheral blood lymphocytes (PBL) expressing the CD8 marker (suppressor cytotoxic T cells) and the CD57 marker (natural killer cells and subset of CD8+ T cells) was highest in infants with acute gastroenteritis, lower in infants without diarrhea, and lowest among those with G. lamblia-associated diarrhea. The level of CD4+ PBL (helper T cells) did not differ significantly among the three groups of children tested. The level of memory, or helper-inducer, CD4+CD29+ PBL was increased markedly in acute gastroenteritis as compared with their level among the other two groups, whereas naive or virgin CD4+CD45RA+ PBL had the reciprocal distribution among the three groups of infants. In contrast to acute gastroenteritis from other causes, G. lamblia-associated diarrhea did not elicit changes in lymphocyte subsets.