Expression of high affinity receptors for murine interleukin 4 (BSF-1) on hemopoietic and nonhemopoietic cells.

Abstract

In this report a method for the affinity purification and radiolabeling of recombinant mouse interleukin (IL)-4 is described. It is shown on the basis of several criteria that IL-4 retains full biologic activity after radioiodination and can therefore be used as a valid model for measuring the binding characteristics of native IL-4. By using Scatchard plot analysis of equilibrium binding data, it is demonstrated that 125I-IL-4 binds to a high affinity cell surface receptor which is expressed by both hemopoietic and nonhemopoietic cells. The dissociation constant for 125I-IL-4 (Kd = 20 to 60 pM) corresponds to the concentration of IL-4 which gives 50% biologic activity (i.e., 10 to 30 pM). Binding of 125I-IL-4 is rapid (t1/2 of 2 min), whereas dissociation occurs at a slow rate (t1/2 approximately 4 hr). The IL-4 receptor shows a high degree of specificity. Whereas unlabeled mouse IL-4 competed with mouse 125I-IL-4 in an equimolar fashion for binding to IL-4 receptors, several other lymphokines, including mouse IL-2, IL-3, interferon-gamma, granulocyte-macrophage colony-stimulating factor, and human IL-1, IL-2, and IL-4 were unable to inhibit, even at molar excesses of 400 to 800-fold. At 37 degrees C, 125I-IL-4 is rapidly internalized (approximately 200 molecules/cell/min) by HT-2 cells, with at least 85% of cell surface receptors being functional in this respect. Receptors for IL-4 were found to be expressed by subclasses of T and B cells, mast cells, macrophages, and by cells of the myeloid and erythroid lineages. This wide distribution of receptor expression closely matches the known spectrum of biologic activities of IL-4, including proliferation and/or differentiation of T and B cells, mast cells and granulocytes, and induction of macrophage antigen-presenting capacity. IL-4 receptors were also found on a variety of nonhemopoietic cells such as cloned stromal cell lines from the bone marrow, spleen, thymus, and brain, and on muscle, brain, melanoma, fibroblast, and liver cells. Indeed, only 5 of more than 90 cell types tested have undetectable numbers of IL-4 receptors. The biologic effects of IL-4 on nonhemopoietic cells have not yet been reported and await elucidation.

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

“…Although early IL‐4/IL‐13 engineering campaigns focused on asthma and allergy applications, later work focused on engineering these cytokines as cancer‐targeted therapies. These efforts were based on detection of IL‐4Rα overexpression in human leukemias, lymphomas, and various solid cancers; these cells could in fact be directly targeted using hIL‐4 223–225 . To harness hIL‐4's cancer‐specificity for therapeutic purposes, a fusion protein of hIL‐4 and Pseudomonas exotoxin A (PE) was engineered to create an anticancer agent (Figure 3B).…”

“…These efforts were based on detection of IL-4Rα overexpression in human leukemias, lymphomas, and various solid cancers; these cells could in fact be directly targeted using hIL-4. [223][224][225] To harness hIL-4's cancer-specificity for therapeutic purposes, a fusion protein of hIL-4 and Pseudomonas exotoxin A (PE) was engineered to create an anticancer agent (Figure 3B). The initial fusion protein exhibited cytotoxicity on a variety of cancer cell lines, but had 15-20 fold weaker affinity compared to unfused hIL-4.…”

Molecular and cellular factors determining the functional pleiotropy of cytokines

“…Longlived complexes, on the other hand, survive the acidic endosomal pH and continue trafficking through the endosomal compartment increasing their chances of finding additional signalling molecules that contribute to fine-tuning their responses. [194][195][196][197]. This has precluded us from studying endogenous cytokine-receptors in live cells and forced us to resort to over-expression studies that may not reflect the real biology of these receptors.…”

The perplexing role of RAGE in pulmonary fibrosis: causality or casualty?

“…[114][115][116] Dupilumab targets both the type 1 and type 2 IL-4R which are primarily present in immune cells and structural cells, respectively. 117,118 IL-4Rα is able to target both IL-4 and IL-13 and block signaling in both structural and immune cells, both of which are key players in asthma and IPF. Therefore, it may be suitable to investigate the effectiveness of dupilumab in models of IPF, with hope that it may be effective in IPF, as seen with eosinophilic asthma (Figure 2).…”