Cutaneous Innate Immunity
Steven B. Hoath, Professor of Pediatrics in the Division of Neonatology and Medical Director, Skin Sciences Institute, of the Cincinnati Children’s Hospital Medical Center, Cincinnati, U.S.A. introduced his presentation by stressing the magnitude of the global problem of relatively unchanged high neonatal mortality rates and the possibility that simple, inexpensive interventions may help alleviate the dangers faced by neonates (Figure 5.1). 32 per cent of neonatal deaths in developing countries are due to infection and there may be simple means by which this might be reduced. Dr. Hoath then went on to present information about the role of the skin in the prevention of infections in newborn infants.
Innate immunity differs from adaptive immunity in that it is present without previous antigen exposure (Figure 5.2). It is clear that resistance to infection occurs at the interface between the environment and the body: i.e. the respiratory tract, the gastrointestinal tract and the skin (Figure 5.3).
The skin as a barrier to infection includes a physical barrier and antimicrobial substances and cellular immune mechanisms (Figure 5.4). The structure of skin is shown in Figure 5.5 and its innate immune mechanisms are summarized in Figure 5.6. The importance of the outermost layer of the skin (i.e. the stratum corneum) is often underappreciated.
The skin of the premature infant is not fully developed (Figure 5.7) when compared to that of the full term infant (Figure 5.8). Therefore, it follows that the difference in structure will be associated with a reduction in innate immunity in the skin of the premature infant.
Vernix caseosa is a complex proteolipid material which covers the skin of the third trimester foetus and newborn infants (Figure 5.9). Its features and microscopic appearance are shown in Figures 5.10 and 5.11.There is now considerable evidence that Vernix caseosa is a multifunctional skin cream containing both anti-oxidants (alpha tocopherol) and a plethora of antimicrobial peptides (Figures 5.12 and 5.13). Biologically, vernix provides a prototype for the development of skin-based neonatal therapies (Figure 5.14) as discussed in Dr. Darmstadt’s presentation.
Increasing awareness of the multiple roles of the skin in primary care delivery (Figure 5.15) supports ongoing research into novel methods of infection control and other practical ways to improve child health in international settings.