There is a strong relationship between nutritional status and resistance to infection. This relationship must receive attention more especially as human being is young. Newborns and infants have some immunological immaturity in regard to systemic immunity as well as local (particularly intestinal), immune defense. Malnutrition is an aggravating factor vis a vis such an immunodeficiency. It modifies the regulating activities of the different lymphocyte populations, of the macrophages, of the complementary system. These disorders are bound to energy, proteins, vitamins and mineral deficiencies. But many metabolic phenomenons have still to be explored, as well as the effect of such a dysimmunity on immunization. Bowel epithelial cells, cross-roads between immunity and nutrition, seem to be the point we ought to select in order to dislocate the infection--malnutrition couple.