Possible involvement of Shc in IL-4-induced germline epsilon transcription in a human B cell line

Engineering the IL-4/IL-13 axis for targeted immune modulation

The structurally and functionally related interleukin-4 (IL-4) and IL-13 cytokines play pivotal roles in shaping immune activity. The IL-4/IL-13 axis is best known for its critical role in T helper 2 (Th2) cell-mediated Type 2 inflammation, which protects the host from large multicellular pathogens, such as parasitic helminth worms, and regulates immune responses to allergens. In addition, IL-4 and IL-13 stimulate a wide range of innate and adaptive immune cells, as well as non-hematopoietic cells, to coordinate various functions, including immune regulation, antibody production, and fibrosis. Due to its importance for a broad spectrum of physiological activities, the IL-4/IL-13 network has been targeted through a variety of molecular engineering and synthetic biology approaches to modulate immune behavior and develop novel therapeutics. Here, we review ongoing efforts to manipulate the IL-4/IL-13 axis, including cytokine engineering strategies, formulation of fusion proteins, antagonist development, cell engineering approaches, and biosensor design. We discuss how these strategies have been employed to dissect IL-4 and IL-13 pathways, as well as to discover new immunotherapies targeting allergy, autoimmune diseases, and cancer. Looking ahead, emerging bioengineering tools promise to continue advancing fundamental understanding of IL-4/IL-13 biology and enabling researchers to exploit these insights to develop effective interventions.

Redox regulation of interleukin-4 signaling

The physiologic control of cytokine receptor activation is primarily mediated by reciprocal activation of receptor-associated protein tyrosine kinases and protein tyrosine phosphatases (PTPs). Here, we show that immediately after ligand-dependent activation, interleukin (IL)-4 receptor generated reactive oxygen species (ROS) via phosphatidylinositol 3-kinase-dependent activation of NAD(P)H oxidase (NOX)1 and NOX5L. ROS, in turn, promoted IL-4 receptor activation by oxidatively inactivating PTP1B that physically associated with and deactivated IL-4 receptor. However, ROS were not required for the initiation of IL-4 receptor activation. ROS generated by other cytokine receptors, including those for erythropoietin, tumor necrosis factor-alpha, or IL-3, also promoted IL-4 signaling. These data indicate that inactivation of receptor-associated PTP activity by cytokine-generated ROS is a physiologic mechanism for the amplification of cytokine receptor activation in both cis and trans, revealing a role for ROS in cytokine crosstalk.

IGH switch breakpoints in Burkitt lymphoma: exclusive involvement of noncanonical class switch recombination

Most chromosomal t(8;14) translocations in sporadic Burkitt lymphomas (BL) are mediated by immunoglobulin class switch recombination (CSR), yet all tumors express IgM, suggesting an incomplete or exclusively monoallelic CSR event. We studied the exact configuration of both the nontranslocated IGH allele and the MYC/IGH breakpoint by applying a combination of low- and high-resolution methods (interphase FISH, DNA fiber FISH, long-distance PCR, and Southern blotting) on 16 BL. IGH class switch events involving the nontranslocated IGH allele were not observed. Thirteen cases had MYC/IGH breakpoints in or nearby IGH switch (S) sites, including five at Smu, three at Sgamma and five at Salpha. All eight translocations with a breakpoint at Sgamma or Salpha were perfectly reciprocal, without deletion of Cmu-Cdelta or other CH elements. Internal Smu deletions claimed to be a marker for CSR activity and implicated in stabilization of IgM expression were found in BL but did not correlate with downstream translocation events. This study shows that switch breakpoints in sporadic BL are exclusively resolved by a noncanonical recombination mechanism involving only one switch region.

Differential effect of IL-4 and IL-13 on the expression of recombination-activating genes in mature B cells from human peripheral blood

We examined the expression of recombination-activating genes (RAG-1 and RAG-2) and activation-induced cytidine deaminase (AID) by mature human blood B cells stimulated with anti-CD40 in the presence of IL-4 or IL-13. IL-4 was an effective cofactor for RAG-1 and RAG-2 expression, whereas IL-13 was not. In addition, IL-4-dependent RAG expression combined with AID and IgE expression allowed predominant expression of newly rearranged lambda light chains on IgE+ cells generated from kappa+ cells. Although the magnitudes of IL-4- and IL-13-dependent AID and IgE expression were related to expression levels of binding subunits of the IL-4 and IL-13 receptors, IL-13 was ineffective for light chain replacement in the induced IgE+ cells due to the failure in RAG expression. Our studies using mature blood B cells indicate that IL-4-responsive cells, unlike IL-13-responsive cells, undergo lambda gene rearrangement leading to replacement in parallel with RAG expression and suggest that this replacement may contribute to the regulation of affinity maturation of IgE antibodies.

Ketoconazole suppresses interleukin-4 plus anti-CD40-induced IgE class switching in surface IgE negative B cells from patients with atopic dermatitis

We previously reported that antimycotic agent ketoconazole suppressed interleukin-4 production in T cells from patients with atopic dermatitis. We herein studied if ketoconazole may suppress B cell IgE class switching. Interleukin-4 plus anti-CD40-induced IgE secretion was enhanced in peripheral blood surface IgE- B cells from atopic dermatitis patients compared to those from normal donors, and the secretion was inhibited by ketoconazole. Ketoconazole suppressed interleukin-4 plus anti-CD40-induced germline and mature epsilon transcripts in surface IgE- B cells. Ketoconazole also inhibited interleukin-4 plus anti-CD40-induced activation of germline epsilon promoter in human Burkitt lymphoma Ramos cells. The regions -171/-155 bp containing CCAAT/enhancer-binding protein element and -155/-109 bp containing Stat6 and nuclear factor kappaB elements were required for the ketoconazole-induced inhibition of the germline epsilon promoter activity. Ketoconazole inhibited interleukin-4 plus anti-CD40-induced enhancer activities of CCAAT/enhancer-binding protein and nuclear factor kappaB, and those of composite elements of CCAAT/enhancer-binding protein/Stat6 or of Stat6/nuclear factor kappaB, but did not alter that of Stat6 in Ramos cells. cAMP analog reversed the inhibitory effects of ketoconazole on interleukin-4 plus anti-CD40-induced IgE secretion, germline and mature epsilon transcripts, and epsilon germline promoter activation. Interleukin-4 plus anti-CD40 increased intracellular cAMP by activating cAMP-synthesizing adenylate cyclase in surface IgE- B cells, and the increase was greater in the cells from atopic dermatitis patients than in those from normal donors. Ketoconazole suppressed interleukin-4 plus anti-CD40-induced activation of adenylate cyclase in surface IgE- B cells. These results suggest that ketoconazole may suppress interleukin-4 plus anti-CD40-induced B cell IgE class switching by inhibiting cAMP signal, and stress its prophylactic effects on allergic diseases.

PKCdelta and zeta mediate IL-4/IL-13-induced germline epsilon transcription in human B cells: a putative regulation via PU.1 phosphorylation

We have investigated the role of PKC isozymes in the function of IL-4 and IL-13 in human B cells. In a Burkitt's B lymphoma cell line, DND39, IL-4 induced the translocation of PKCdelta and zeta from the cytosol to the membrane fraction. The activation of germline epsilon promoter by IL-4 was abrogated not only by the expression of dominant negative mutants of PKCdelta and zeta but also by isozyme-selective PKC inhibitors, rottlerin and PKCzeta pseudosubstrate peptide. These inhibitors also suppressed IL-4/IL-13-induced germline epsilon transcription in the IL-13Ralpha1-transfected DND39 cells as well as in normal human B cells, but had no influence on the induction of CD23b in the latter cells. As a downstream event of PKC, we found threonine phosphorylation of PU.1 in IL-4-stimulated DND39 cells. This phosphorylation was suppressed by the PKC inhibitors, although STAT6 activation was unaffected. These results suggest that, in human B cells, IL-4/IL-13 utilize PKCdelta and zeta for the STAT6-independent signaling pathway and thereby modulate the transcriptional activity of PU.1.