Time of appearance of immunoglobulin-containing cells in the mucosa of the neonatal intestine.

In 46 intestinal specimens from infants 2 hr to 6 months old, the numbers of immunoglobulin-containing cells were counted by the direct immunofluorescent or direct immunoperoxidase technique. A restudy was made of biopsy specimens taken for diagnostic purposes, 34 from the rectum and 3 from the transverse colon of 30 infants at the Children's Hospital, Helsinki in 1971-1977, and in addition, of autopsy material recently collected from the intestines of 9 infants. Up to the age of 12 days, no immunoglobulin-containing cells were seen. A small number (1 to 2) of IgM-containing cells was seen in the lymph nodes of the 2 earlier specimens taken at the ages of 6 and 12 days. A rectal specimen from a 12-day-old infant showed 24 IgA- and 60 IgM-containing cells/mm2. In rectal specimens of infants less than 1 month old, the mean number of IgM-containing cells (26/mm2) was higher than that of IgA-containing cells (14/mm2), but older infants had a significantly higher mean number of IgA-containing cells (P < 0.01). The mean number of IgM-containing cells was the same in children 1 to 3 months (53 cells/mm2) and 3 to 6 months of age (59 cells/mm2), whereas the mean number of IgA-containing cells increased with age up to 6 months (112 and 163 cells/mm2). The youngest infant who had IgG-containing cells was 13 days old, although positive staining of intercellular spaces in the lamina propria and of the capillary endothelium by anti-IgG serum was observed in all specimens. The mean number of IgG-containing cells was low (5 cells/mm2) in all age groups. Sparse IgE-containing cells (less than 12 /mm2) were seen in 4 of the 46 specimens. In 5 patients, 2 or 3 consecutive specimens were available for the study; in these, the increase in the numbers of IgA- and IgM-containing cells was similar to the mean increase in cell numbers for the series as a whole.