Differential display analysis of gene expression during the induction of mucosal immunity

One approach to understanding the physiologically relevant events during the induction of an immune response is to identify genes that are expressed when the immune system first encounters antigen. Such an investigation requires a naive but fully functional immune system, and the fetal lamb provides these conditions during the last trimester of gestation. 'Intestinal segments,' containing a jejunal Peyer's patch, were surgically prepared in fetal lambs (>120 days gestation) and individual 'intestinal segments' were injected with either culture medium or infectious bovine rotavirus. Peyer's patch tissue was collected 18 h postinfection. Histology and virus culture confirmed that bovine rotavirus had infected the mucosal epithelium. RNA was extracted from jejunal Peyer's patch tissue and mRNA differential display was used to identify genes expressed following rotavirus infection. Ten cDNAs were identified by differential display and these cDNAs were isolated, cloned, and sequenced. One of the cDNAs sequenced, displayed homology to the gene encoding the sperm surface protein Sp17. Differential expression of this gene in antigen-exposed jejunal Peyer's patches was confirmed by Northern blot and RT-PCR. The complete sequence for sheep Sp17 mRNA was obtained from a lambda cDNA library, prepared from the jejunal Peyer's patch of a young lamb. Sp17 expression was detected by RT-PCR in a variety of mucosa-associated lymphoid tissues but not in primary or other secondary lymphoid tissues. Thus, the fetal lamb model may be appropriate for identifying genes relevant to mucosal immunity.