Expression of Ig genes during three early developmental stages. PCR amplifications of each primer set were performed for 30, 35 and 40 cycles. Two individuals were studied in each stage. Four immune related genes, il-1β1 (IL-1β1), tnf-α (TNF-α), mx (Mx) and cox-2 (COX-2), were also examined. Ubiquitin is an internal control.