B-cell development in lamina propria of the large intestine: influence of age and t-cell densities

The development of B-cells and immunoglobulin-isotype and IgA subclass-posi tive cells in the lamina propria of the large intestine during infancy was investigated. Biopsy specimens from 36 infants, taken for diagnostic purpos es, were available. All samples showed normal morphology. Monoclonal antibo dies to CD22, IgA, IgA1, IgA2, IgM and IgG and a peroxidase method were use d to demonstrate positive cells in the cryostat sections. Cell densities we re counted from a known area. T-cells had been measured in a previous study using the same specimens. The density of CD22+ cells was already high in i nfants below the age of 1 month and increased little with age. Four specime ns from infants below the age of 40 days lacked IgA-, IgA1- and IgA2-positi ve cells. The densities of these cells increased with age; the correlation coefficient between the age and the density of the cells was for IgA: R=0.4 7, p=0.04; for IgA1: R=0.57, p=0.001, and for IgA2: R=0.34, p=0.04. The den sities of IgG- and IgM-positive cells remained unchanged with age. The nega tive correlation between density of IgG+cells and CD8+ cells in the lamina propria (R=- 0.43, p=0.01) was significant. Strong local stimulation result s in early accumulation of CD22+, IgM+ and IgG+ cells in the large intestin e, but little change takes place after the first few days of life. The term inal differentiation to IgA-positive cells is slowest, and this population showed significant developmental change.