Both human SP-A1 and SP-A2 genes are expressed in small and large intestine

The human SP-A locus consists of two functional genes and one pseudogene, a nd SP-A is shown to play a role in local host defense and the regulation of inflammation in lung. Because the intestine, like the lung, is constantly exposed to foreign and potentially harmful substances, we investigated the hypothesis that both human SP-A genes are expressed in intestine. We demons trate that both SP-A genes are expressed in human small and large intestine . The presence of SP-A mRNA in human intestine was detected by reverse tran scription-polymerase chain reaction (RT-PCR), Northern blot analysis, and i mmunohistochemistry. The size of intestinal SP-A mRNA is the same as that i n human lung, but the level of expression, compared with that in the lung, is very low in both the small and large intestine. Immunohistochemical anal ysis revealed positive reactivity for SP-A in a subgroup of epithelial cell s in the intestine. Expression of both SP-A1 and SP-A2 genes was establishe d by gene-specific PCR amplification, PCR-based converted RFLP discriminati on, and direct sequencing of RT-PCR products. We speculate that SP-A in the intestine plays a role in local host defense and inflammation.