To search for rapid changes in gene expression following pre-BCR activation, we performed DNA microarray analysis of activated pre-B cells with and without anti-m heavy chain treatment for 3 hour.The expression of only small subset of genes differed significantly. Overall design: The mouse bone marrow derived pre-B cells were grown with IL-7 on limiting amounts of S17 stromal cells and activated by incubation with goat F(ab’)2 anti-mouse μ heavy chain (Southern Biotechnologies) at 5 μg/ml for 3 hour.