[Characteristics of immunoreactivity in neonates and young children. Review of the literature].

Newborns and infants are particularly susceptible to infections, and this appears to be due to deficient immuneresponsiveness. The survey of the pertaining literature (95 references) reveals the particularities of newborns' and infants' immune responses. After the brief survey of basic immunological terms, innate (natural) and acquired (specific), systemic and local (regional) immune responses are described. Characteristics of cellular [leukocytes, polymorphonuclears, neutrophils, eosinophils, mast cells, monocytes, macrophages, natural killer (NK-) cells] and humoral (complement system, fibronectin, C-reactive protein) components of innate immunity are surveyed. Follows the analysis of cellular and humoral participants in specific immune responses: antigen presenting cells (macrophages, dendritic cells), B cells (immunoglobulins), T cells (TCR-1 T cells, TCR-2 T cells). Finally, the characteristics of local immunity are described. The presented overview of the immune responses reveals a partial immune system's immaturity (maturational deficiency) in newborns and infants.