Maternal cigarette smoking and hla-dr expression in alveolar macrophages in infants

Macrophages are important in host defences in the lung via phagocytic activity, antigen presentation and secretion of inhibitory and pro-inflammatory mediators. The expression of HLADR, a marker of immune function, on alveolar macrophages, is reduced in cigarette smokers and this may alter their immune function. We hypothesised that infants exposed to maternal cigarette smoke will also have reduced expression of HLA-DR on alveolar macrophages. To examine this we compared HLA-DR expression using immunohistochemistry on lung tissue from infants (n=5) who died of SIDS who were exposed to maternal cigarette smoke ( 10 cigarettes a day) with infants (n=6) who also died of SIDS but had no maternal cigarette smoke exposure. Maternal smoking history was obtained by direct interview within 4 weeks of the infants death. We determined the density of alveolar macrophages in the lung by point counting. Points falling on alveolar walls and on HLA-DR + and - alveolar macrophages were counted in five random high power fields (x400). Total macrophages, as a percent of all points counted, and the percent of those macrophages with HLA-DR + staining are shown in the table. Results are expressed as mean SE. Gestation Birth weight age Macrophages HLA-DR + (week) (kg) (mths) (%) (%) Non smoke 40 + 0.5 3.8 + 0.2 6 + 3 9%+ 2 40%+ 8 Smoke exp 40 + 0.3 3.3 + 0.3 5 + 1 14%+ 2 28%+ 4 p value 0.8 0.2 0.7 0.09 0.2 These findings suggest in infants, that the number of alveolar macrophages and the expression of HLA-DR is not altered by maternal cigarette smoking.