Coexpression of the interleukin-13 and interleukin-4 genes correlates with their physical linkage in the cytokine gene cluster on human chromosome 5q23-31

Interleukin-13 (IL-13) and IL-4 are cytokines produced by T cells that are encoded by the q23-31 region of human chromosome 5. To investigate the regulation of IL-13 gene expression by T cells, we isolated and sequenced the human IL-13 gene, analyzed its 5'-flanking region for potential transcriptional activation elements, and examined its expression in nontransformed T-lineage cell populations. The human IL-13 gene was located 12.5-kb upstream of the IL-4 gene and 2-kb downstream of a CpG island. The IL-13 gene 5' flank region included a segment with sequence homology to P elements of the IL-4 promoter involved in transcriptional activation in T cells. Mutation of the IL-13 P element site significantly reduced IL-13 promoter activity in response to T-cell activation. Oligonucleotides containing the IL-13 or IL-4 P element sites specifically bound the transcriptional activator protein, nuclear factor-activated T cells, preformed (NF-ATp), when incubated with nuclear protein extracts from activated T cells. Similar to IL-4, IL-13 mRNA expression was highest in T-cell populations enriched for cells that had previously been primed in vivo or in vitro, indicating that priming increases the expression of the IL-13 and IL-4 genes in a coordinate manner. Because the primed T cells contain higher levels of nuclear NF-ATp, capable of binding to P elements of the IL-4 and IL-13 promoters, than do freshly-isolated T cells, the NF-AT-binding P elements are attractive candidates to mediate the coordinate expression of these two cytokine genes.

Leishmania major: nature of immunity induced by immunization with a mutagenized avirulent clone of the parasite in mice

A chemically mutagenized avirulent form of Leishmania major was used to immunize BALB/c and C57B1/6 mice against challenge with virulent L. major. Immunity was elicited when the avirulent parasite was injected intravenously or intraperitoneally, but not subcutaneously. In fact, the latter route of immunization sometimes resulted in exacerbation of a subsequent infection with virulent L. major. Mice immunized with avirulent L. major developed upon challenge with virulent L. major cutaneous lesions which were significantly smaller and contained substantially fewer parasites than lesions on control nonimmune animals. Finally, the protection conferred by immunization with avirulent L. major could be adoptively transferred with T cells of the CD4+ lineage but not the CD8+ lineage.