Selective induction of delayed hypersensitivity T-effector and T-suppressor lymphocytes in vitro by haptenized bone marrow-derived macrophages

Alternatively activated macrophages actively inhibit proliferation of peripheral blood lymphocytes and CD4+ T cells in vitro

We compared the immunological functions of interferon-gamma (IFN-gamma)-induced, classically activated macrophages (caM phi) and of interleukin-4 (IL-4)- and glucocorticoid-induced, alternatively activated macrophages (aaM phi) in a human co-culture system in vitro. Proliferation of peripheral blood leucocytes (PBL) or CD4+ T cells mediated by optimal doses of phytohaemagglutinin (PHA) or concanavalin A (Con A) was only marginally influenced by caM phi, but was strongly inhibited by aaM phi. The degree of lymphocyte proliferation sustained in the presence of caM phi was gradually reduced in a dose-dependent fashion by the addition of aaM phi. Flow cytometric analysis revealed that expression of costimulatory molecules such as CD11a, CD40, CD54, CD58, CD80 and CD86 did not vary significantly between caM phi and aaM phi and was low for CD58, CD80 and CD86. As shown by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, IL-10 was expressed in caM phi, aaM phi and control macrophages; the level of expression of IL-10 was slightly enhanced in aaM phi. Neither neutralizing anti-IL-10 antibodies, indomethacin nor NG-monomethyl-L-arginine (NMMLA) was able to reverse aaM phi-mediated inhibition of lymphocyte proliferation. Of several agents interfering with various second messenger pathways, cAMP and the Ca(2+)-ionophore A23187 inhibited differentiation of cultured human monocytes into phenotypically mature aaM phi expressing MS-1 high molecular weight protein (MS-1-HMWP) and RM 3/1 antigen, and prevented the suppressive action of aaM phi on lymphocyte proliferation. In conclusion, these results who that aaM phi actively inhibit mitogen-mediated proliferation of PBL and CD4+ T cells independently of the expression of costimulatory molecules and of IL-10, NO or prostaglandin synthesis, and that inhibition of phenotypic differentiation of aaM phi is paralleled by a lack of functional maturation. Thus, fully matured aaM phi may be functional in down-regulating CD4+ T-cell-mediated immune reactions by an as yet unknown mechanism.

Immunologic effects of interferon

Interferons can be defined as a family of induced proteins sharing the capacity to exert pleiotropic effects on cell functions and to render cells resistant to virus infection. They are activating genes coding for a number of enzymes, most of which have not yet been characterized, and also by enhancing the synthesis of cell surface components. This enables interferons to modulate the immune response at different levels. This article will focus on the effects of interferon on antigen presentation, regulation of the immune response, activation of macrophage functions, and on its role in the pathogenesis of some diseases.

Phenotypic dynamics of macrophage subpopulations during human experimental gingivitis

The purpose of the present study was to investigate whether functionally different macrophages are present in clinically healthy gingiva and during human experimental gingivitis. Eight male probands were introduced to an oral hygiene program until all reached mean Plaque and Gingival Index scores approaching zero. During the following 19 days all oral hygiene was abandoned. At d -14, 0, 2, 4, 7, 11 and 19 clinical indices and gingival biopsies were taken. Cryostat sections were incubated with monoclonal antibodies against mature macrophages (25F9), inflammatory macrophages (27E10) and anti-inflammatory macrophages (RM 3/1). Positive cells were counted in the inflammatory infiltrate (IF) and the connective tissue (CT). At d -14 elevated numbers of 27E10-positive cells were observed which decreased significantly at d 0 (p less than 0.018) and increased again at d 19 (p less than 0.026). Significant differences in the number of RM 3/1-positive cells were found between d 0 and d -14, 2, 4 and 7 (p less than 0.05) while no differences in the number of 25F9-positive cells were observed throughout this study. It was concluded that experimental gingival inflammation is characterized by the appearance and disappearance of functionally different macrophage subpopulations.

Immunotoxicology today

Immunotoxicology is a science which deals with the effects of physical and chemical agents and other toxic substances on the immune system. The discipline includes study of the detection, occurrence, adverse effects, and mechanisms of chemically-induced immune dysfunction. Many drugs and chemicals are known to compromise the immune response of a host which is extremely vulnerable and sensitive to perturbation by these agents. The consequences of immune dysfunction may be expressed in reduced resistance to infectious and neoplastic diseases, or enhanced hypersensitivity and autoimmunity. The immunomodulating profiles of xenobiotics may be diverse, involving several components of the immune system, or they may selectively compromise an individual compartment of the immune response. Many drugs and chemicals are known to result in immune disregulation in animals, but a paucity of information is available to indicate the effects of xenobiotics on systemic immunity in humans. Epidemiological studies and research designed to assess chemical immunomodulation in man are necessary to confirm animal data. Further, a definitive diagnosis for chemically-induced immune dysfunction must include several etiologies and body organ systems, since a triad of reciprocal interactions exists between the immune, endocrine, and central nervous systems.

Inhibitory effects of interferon-gamma on the T suppressor cell circuit in contact sensitivity

The effects of a partially purified, splenocyte-derived murine interferon (MuIFN-gamma N) and a recombinant IFN-gamma (MuIFN-gamma R) on the T suppressor pathway and on the T effector cells of delayed type hypersensitivity were investigated in a 2,4-dinitrofluorobenzene contact sensitivity model. Various T cell subpopulations, suppressor T cells of afferent and efferent types, and an auxiliary T suppressor cells as well as a T effector cell of delayed type hypersensitivity were induced and the functions assessed in transfer experiments. Confirming the results of earlier experiments obtained with IFN-alpha, beta, the MuIFN-gamma N preparation and the rec. MuIFN-gamma R: enhanced the decreased response in animals sensitized with an antigen overload to an optimal response; inhibited the afferent-acting T suppressor cell in vivo and in vitro; inhibited the Ts-eff response; blocked the auxiliary T suppressor cell response after intravenous injection to recipients of Ts-eff cells on day 0 and 1; and did not suppress the activity of the T effector cell of delayed type hypersensitivity in vivo and in vitro (the MuIFN-gamma R was not tested). We conclude that IFN-gamma preferentially inhibited the T suppressor cell circuit of contact allergy. These results are similar to our observations on the inhibitory effects of a pure interferon-alpha, beta on the regulatory T suppressor cell circuit in contact allergy. Selective suppression of different T subpopulations by IFN-gamma may be an important regulatory mechanism in delayed type hypersensitivity.