HISTAMINE-RELEASING CELLS OF THE NEWBORN - MAST-CELLS FROM THE UMBILICAL-CORD MATRIX AND BASOPHILS FROM CORD-BLOOD

The cellular branch of the immune defence in the newborn has been show n to differ from adults in a number of ways. This report presents new data on the functions of the histamine-secreting cells of the newborn. Mast cells of the newborn were obtained from the human umbilical cord by enzymatic dispersion. The granules of the mast cells of the umbili cal cord were found to contain both chymase and tryptase by immunohist ochemical staining, and the presence of cell-bound IgE on the mast cel l surface was demonstrated by staining sections of umbilical cord with peroxidase-conjugated anti-IgE. The enzymatic dispersion yielded 12,6 60 mast cells per gram umbilical cord (median), range 2,500-60,300 (n= 48). The mast cells were found to constitute 3.1 % of the total nuclea ted cells in the dispersate (median), range 1.5-3.8%. The histamine re lease from these cells was measured using a glass microfibre-based met hod. Both the umbilical cord mast cells and the cord blood basophils r eleased histamine stimulated with anti-IgE, concanavalin A and the cal cium ionophore A23187. In contrast to mast cells from adult tissue, th e phorbol ester TPA was found to be an efficient secretagogue in both mast cells and basophils from the newborn. After maximal stimulation w ith anti-IgE and phorbol ester the quantity of histamine released per millilitre of blood was significantly higher in cord blood than in adu lt blood. The spontaneous histamine release from cord blood basophils was also significantly higher than from adult blood basophils. The mas t cells found in the umbilical cord matrix and the cord blood basophil s represent a readily available source of metabolically active histami ne releasing cells for exploration of the role of histamine-secreting cells in newborn immune defence.