Increased expression of mRNA encoding interleukin (IL)‐4 and its splice variant IL‐4δ2 in cells from contacts of Mycobacterium tuberculosis, in the absence of in vitro stimulation

Abstract

SUMMARYExpression of interleukin (IL)-4 is increased in tuberculosis and thought to be detrimental. We show here that in healthy contacts there is increased expression of its naturally occurring antagonist, IL-4delta2 (IL-4d2). We identified contacts by showing that their peripheral blood mononuclear cells (PBMC) released interferon (IFN)-c in response to the Mycobacterium tuberculosis-specific antigen 6 kDa early secretory antigenic target (ESAT-6). Fresh unstimulated PBMC from these contacts contained higher levels of mRNA encoding IL-4d2 (P=0AE002) than did cells from ESAT-6 negative donors (noncontacts). These data indicate that contact with M. tuberculosis induces unusual, previously unrecognized, immunological events. We tentatively hypothesize that progression to active disease might depend upon the underlying ratio of IL-4 to IL-4d2.

Splice isoforms of human interleukin-4 are functionally active in mice in vivo

“…18 In patients with pulmonary tuberculosis, greater absolute expression levels of both IL-4 and IL-4d2 in blood and lung were associated with more extensive disease. [19][20][21] Expression of IL-4d2 was increased in respiratory tract tissues of patients with asthma, 22 and pulmonary fibroblasts have been reported to alter the IL-4d2 : IL-4 ratio in mast cells in patients with asthma. 23 A relative increase in IL-4 and a decrease in IL-4d2 have been associated with better survival in patients with severe sepsis.…”

Do successful tuberculosis vaccines need to be immunoregulatory rather than merely Th1-boosting?

“…Still more revealing is the observation that expression of IL-4δ2 mRNA is increased in the peripheral blood of healthy donors who have latent TB, as defined by the presence of a positive ELISPOT IFN-γ response to ESAT-6. This has been shown by different methods in Ethiopia and in The Gambia [18,19]. It implies that despite their healthy appearance, people with latent TB are involved in a "battle" between IL-4 and its inhibitor.…”

“…Beijing strains should be particularly good at this [20]. In some individuals, for reasons that we do not yet understand, the effect of the IL-4 will be blocked by a disproportionate rise in IL-4δ2 [18,19].…”

Real-time RT-PCR normalisation; strategies and considerations

“…1 Furthermore, many of the key proteins (eg cytokines and transcription factors) are found in such low abundance that real-time RT-PCR quantification of their mRNAs represents the only technique sensitive enough to measure reliably their expression in vivo. 2,3 Although real-time RT-PCR is widely used to quantitate biologically relevant changes in mRNA levels, there remain a number of problems associated with its use. These include the inherent variability of RNA, variability of extraction protocols that may copurify inhibitors, and different reverse transcription and PCR efficiencies.…”