Steven B. Mizel

Interleukin l and T Cell Activation

The antigen-specific activation of T cells is dependent upon two distinct but interdependent macrophage signals. Macrophages are required to bin^, process, and present antigens in an immunogcnic form to T cells (Schwartz et ul. 1978). This function of the macrophage is genetically-restricted and is a property of an la positive subpopulation of macrophages. The second macfophage-derived T cell activating signal is a Iow molecular weight antigen-non-specific peptide termed interleukin 1 (IL I) (Aarden et al. 1979) that is apparently produced by all macrophages (Oppenheim etal. 1979). As will be discussed in this review, IL I appears to act as a maturational signal, preparing T cells to respond to antigens or secondary mediator signals. One of the major activities of interleukin 1 is to induce the synthesis and secretion of the T cell-derived mitogenic lymphokine, interleukin 2 (IL2) (Farrar et al. 1980b, Smith et al. 1980, Larsson et al. 1980). This link between IL 1 and IL 2 is an essential element in the T cell activation sequence because it involves the conversion of a primary macrophage-derived maturational signal into a secondary T cell-derived proliferative signal that results in the amplification of specific immune responses.

The role of macrophages in the acute-phase response: SAA inducer is closely related to lymphocyte activating factor and endogenous pyrogen

Abstract An increase in the concentration of the acute-phase reactant, serum amyloid A (SAA), following endotoxin treatment, is a consequence of the action of lipopolysaccharide (LPS) on macrophages to produce a monokine, the SAA inducer, which in turn, triggers SAA synthesis by hepatocytes. We have found that murine SAA inducer is closely related, if not identical, to murine lymphocyte activating factor (LAF), otherwise known as Interleukin 1 (IL 1). Furthermore, both rabbit endogenous pryrogen (EP), which is believed to be identical to LAF (IL 1), and human LAF (IL 1), induced elevated SAA concentrations in C3H/HeJ mice. Antiserum previously shown to block both pyrogenic and thymocyte proliferating activities of the species of rabbit EP exhibiting an isoelectric point of pH 7.3 (EP 7), also blocked the SAA inducing activity of EP7. Phenylglyoxal treatment of highly purified murine LAF (IL 1) abrogated both thymocyte proliferating activity and the SAA inducing activity. These studies support and extend previous reports suggesting that within 2 hr of an inflammatory stimulus, macrophages produce a monokine that acts systemically to alter body temperature, activate T cells, and induce hepatic protein synthesis of acute-phase reactants.

Biological Effects of Lymphocyte and Macrophage-Derived Mitogenic “Amplication” Factors

Publisher Summary Both cellular and humoral immune responses are initiated by a very small number of specifically sensitized lymphocytes. Mitogenic factors can potentially amplify that small response through their lymphoproliferative effects. The number of lymphocytes that participate in a specific immune reaction can be expanded through the recruitment of uncommitted lymphocytes by nonspecific mitogenic factors. Mitogenic factors, which have also been called as blastogenic or transforming factors, are operationally defined as the activities that appear in the supernatants of leukocyte cultures and cause lymphocytes to divide and/or synergistically augment cell division induced by other lymphocyte stimulants. Mitogenic factors can potentially be produced by one or more of the cell types in leukocyte cultures, for example, lymphocytes, monocytes, neutrophils, or platelets. Mitogenic or closely related factors can induce lymphokine production and the subsequent recruitment of inflammatory responses involved in the efferent limb of the immune response. Mitogenic amplification factors also cause the maturation of target cells. Maturation presumably is an inevitable consequence of cell division.

Stimulation of fibroblast proliferation and prostaglandin production by purified recombinant murine interleukin 1

Recombinant murine interleukin 1 (IL-1) obtained from a clone of Escherichia coli containing an IL-1 expression plasmid was purified to homogeneity using a sequential extraction procedure and gel filtration chromatography. The purified recombinant IL-1 exhibited a pI of approximately 5.2 and a sp act of 6 X 10(6) units/mg. These values are in agreement with those obtained with natural murine IL-1. The purified recombinant IL-1 enhanced the proliferation of human HEL and WI-38 fibroblasts in a serum-free medium. In addition, IL-1 stimulated fibroblast PGE2 5- to 30-fold over a 24-hr period. The effects of IL-1 on fibroblast activation were obtained with the same concentrations of IL-1 that are effective in the mouse thymocyte assay. These results unequivocally establish the ability of IL-1 to modulate fibroblast proliferation and function.

A Recombinant Flagellin-Poxvirus Fusion Protein Vaccine Elicits Complement-Dependent Protection Against Respiratory Challenge with Vaccinia Virus in Mice

Bacterial flagellin is a potent adjuvant that enhances adaptive immune responses to a variety of protein antigens. The vaccinia virus antigens L1R and B5R are highly immunogenic in the context of the parent virus, but recombinant forms of the proteins are only weakly immunogenic. Therefore we evaluated the humoral response to these antigens in mice when flagellin was used as an adjuvant. Flagellin-L1R and flagellin-B5R fusion proteins were more potent than flagellin, L1R, and B5R as separate proteins. At least three immunizations with flagellin-L1R and flagellin-B5R fusion proteins were required to confer protection in mice against challenge with vaccinia virus. Immune mice exhibited only limited signs of disease following challenge. Additionally, virus neutralization titers correlated with protection. Depletion of complement using cobra venom factor resulted in a marked decrease in the survival of immunized mice after challenge with vaccinia virus. Our results are consistent with the conclusion that flagellin-L1R and flagellin-B5R fusion proteins are effective in eliciting protective immunity against vaccinia virus that is dependent, in large part, on complement.

Molecular signals in antigen presentation. I. Effects of interleukin 1 and 2 on radiation-treated antigen-presenting cells in vivo and in vitro.

In order to clarify the nature of the defect in the process of antigen presentation caused by uv radiation, low-density spleen cells were used as a potent APC source in a hapten-specific cytolytic T-cell (Tc) system. It was demonstrated that IA+ weakly adherent low-density spleen cells, when directly coupled with azobenzene arsonate (ABA), led to the activation ABA-specific Tc. When these APC were exposed to uv radiation (12 J/m2/sec) for 30 sec, their ability to lead to Tc activation was markedly inhibited. The defect imposed by uv radiation could be specifically bypassed by the addition of small amounts of homogeneous IL-1 or IL-2. This led to the specific activation of ABA-reactive H-2-restricted Tc. The purified IL-1 was also found to bypass the systemic defect imposed in vivo by external uv radiation of mice. This may indicate a potential therapeutic role for IL-1.

[37] Murine interleukin 1

Publisher Summary This chapter describes the basic protocols for the production and purification of IL-1 from the P388D 1 macrophage cell line, along with assays used to quantitate IL-1 activity. A basic protocol for generating goat antibodies to IL-1 is also explained. Interleukin I (IL-1) 1 is a polypeptide of 12,000 to 17,000 molecular weight that functions as a major communication signal between the macrophage and other cell types that are involved in immune and inflammatory responses. This polypeptide is produced by peripheral blood, peritoneal, alveolar, and placental macrophages. In addition, a number of IL-l-producing glioma and keratinocyte tumor cell lines are described. Murine IL-1 was initially purified to homogeneity as a result of (1) the use of the P388D1 murine macrophage cell line and (2) the use of a superinduction protocol for producing relatively high levels of IL- 1. The chapter further discusses the purification of murine interleukin 1.

Molecular Studies on Murine Interleukin 1

Our understanding of IL 1 biology has been accompanied by dramatic advances in IL 1 biochemistry and molecular biology. In 1981, murine IL 1 was first purified using standard chromatographic procedures (1). Subsequently anti-IL 1 antibodies were generated and used to purify murine IL 1 with a significant increase in overall yield of active protein (2). Using anti-IL 1 antibodies, Giri et al. (3) demonstrated that murine IL 1 is initially synthesized as a 33,000 molecular weight precursor that is enzymatically cleaved to the lower molecular weight forms detected in the culture medium of stimulated cells. More recently, human IL 1 has been purified from the conditioned medium of cultures of stimulated peripheral blood mononuclear cells (4–6) as well as a monocytic leukemia cell line (7). However, a major breakthrough in IL 1 research was achieved with the cloning, sequencing, and expression of cDNAs for murine (8) and human (9–11) IL 1. These studies revealed the existence of at least two forms of human IL 1, termed IL 1α (pI 5) and IL 1β (pI 7).