Impaired differentiation of Ig A-B cell precursors in the Peyer's patches of protein depleted rats.

The aim of this study has been set on Ig A plasma cell precursors that are found in the Peyer's patches. In a previous work it has been shown that protein deficiency at weaning led to the presence in the Peyer's patch of very immature B cells, mostly cu+ su- cells. In this report we demonstrate the c mu+ s mu- cells comprise a (c mu OX7)+ s mu- cell population that is predominant in the protein-deprived rats (41.5 versus 16.8 in 39 day-old control rats). Protein refeeding reinitiates the differentiation as follows: (a) the (c mu OX7)+ s mu- cell population was able to differentiate to (cs mu+ as in the normal Peyer's patch (53.6 versus 44.9 in 39 day-old control rats); (b) the switching of sIg M-bearing cells to sIg A-bearing cells occurs in a restricted pattern; only 27.9 versus 47.6 in the 60 day-old control rats; (c) concomitantly, protein-refed rats showed a low absolute number of W3/13+ and W3/25+ T cells. Therefore, this experimental model of immunodeficiency provides further evidence that specialized T helper cells or their soluble factors are needed for Ig A-B cell differentiation "in vivo."