Fetal and Infant Immune System
- (passage of maternal antibody -IgG only)
- Active Immunity
- Beginning at 8 weeks gestational age (GA)
- IgG levels correlate with GA:
- low until 20 weeks
- by 40 weeks, it doubles that of 32 wks
- B cells and T cells present by 14 weeks’ GA.
- Relatively sterile environment in utero.
- There is an enormous unchallenged capacity.
Neonatal and Infant Immunity
- Instant challenge.
- Within hours, GI tract heavily colonized.
Passive Immunity (maternally acquired antibodies)
- Circulating placental IgG lasts 6 months or longer.
- Secretory IgA in breast milk and colostrum
- B cell responses are good.
- Until two years of age, children do not respond well to T cell-independent antigens (i.e., polysaccharides)
- Full T cell subsets.
- Infants respond well to T cell-dependent antigens (i.e., proteins).
Source: BCCDC http://www.bccdc.ca/NR/rdonlyres/E3794F78-3B8A-41FD-B36C-53055D314B6E/0/SectionVIII_PrinciplesofImmunology_September.pdf