Proliferation of dendritic cells in the bronchioles of sudden infant death syndrome victims.

Sudden Infant Death Syndrome (SIDS) victims have significantly thickened bronchiolar walls with increased mononuclear cells in the adventitia. An immunohistochemical study was performed on 25 SIDS and 18 aged-matched control infants to characterize these cells. The panel of antibodies included alpha-1-antitrypsin, lysozyme, actin, vimentin, Leu M1, NSE, S-100, Leu 6, bombesin, serotonin, anti-substance P, vasoactive intestinal peptide, MAC 387, and Factor XIIIa. The bronchiolar cells stained with S-100 antibody and demonstrated slender processes similar to dendritic cells, such as Langerhans' cells, and interdigitating reticulum cells, present in normal tissues as well as in certain tumors and inflammatory diseases. Manual counting of the S-100 positive cells and fibers revealed both of these to be significantly increased in SIDS infants as compared to age-matched control infants. Morphologically, the bronchiolar dendritic cells closely resembled Langerhans' cells and therefore may have similar immunologic functions, such as antigen presentation and viral and neoantigen immunosurveillance. We hypothesize that the proliferation of these dendritic cells in SIDS victims is a result of exposure to environmental antigens, resulting in a thickening of the bronchiolar walls, narrowing of the lumen, and reduction in airflow, thus causing a chronic or persistent hypoxia.