Immunohistochemical localization of Forssman glycosphingolipid-positive macrophages and reticular cells in murine lymphoid tissue

Markers of mouse macrophage development detected by monoclonal antibodies

In this review, we present and discuss a selected panel of antibody-defined markers expressed during different stages of mouse macrophage development. We distinguish four categories of markers, which are characteristic of: (1) macrophage precursors and immature macrophages (ER-MP12, ER-MP20, ER-MP54, ER-MP58); (2) mature macrophages in general (F4/80, BM8, Mac-1, Mac-2, ER-BMDM1); (3) macrophage subsets (ER-HR3, ER-MP23, ER-TR9, Forssman antigen, MOMA-1, MOMA-2, Monts-4, SER-4), and (4) IFN-gamma-stimulated macrophages (H-2Ia, LFA-1, ICAM-1, 158.2, MBR-2, TM-2, TM-4, and TM-5). It should be noted that many of the markers in this last category are inducible by other stimuli as well. The rigid classification of markers into four separate groups should be regarded as a digitalization of a continuum, thus inevitably implicating a simplification of the complex phenotypic changes that occur during mononuclear phagocyte development. Nevertheless, the current selection of antibodies against markers for different developmental stages of macrophages constitutes an important tool for characterization of mouse macrophages which participate in various biological processes.

The functional state of follicular dendritic cells in severe combined immunodeficient (SCID) mice: role of the lymphocytes

In the present study, we have investigated the capacity of follicular dendritic cells (FDC) to trap immune complexes (IC) in the splenic white pulp of severe combined immunodeficient (SCID) mice and the influence of lymphocyte transfer on FDC function. FDC are absent in the splenic white pulp of naive SCID mice as revealed by in vitro IC trapping assay. One week after transfer of syngeneic lymphocytes, functional FDC with complement receptors appeared in the primary follicles coincident with B cell segregation, and IC were trapped on those FDC in a complement-dependent manner. Next, we immunized the reconstituted SCID mouse to see whether another type of FDC could be induced in the secondary follicle. Antigenic stimulation induced FDC with an additional capacity to capture IC via FcR gamma II. As seen in immunocompetent mice, this type of FDC was located only in the light zone of the secondary follicle. The newly generated FDC did not carry H-2 antigen of transferred lymphocytes from F1 mice. In SCID mice, in which normally no functional FDC are detectable, the microenvironments of the splenic white pulp have a capacity to develop and differentiate normally after transfer of lymphocytes. Apparently, the generation of functional IC-trapping FDC causes the induction of complement receptor(s) and Fc receptor on meshwork cells, which requires the presence of the lymphocytes.

Surface expression of Forssman glycosphingolipid antigen on murine bone marrow-derived macrophages is subject to both temporal and population-specific regulation and is modulated by IL-4 and IL-6

The Forssman glycolipid antigen (Fo) has been shown to be a differentiation marker for mouse macrophages both in vivo and in vitro. In order to determine whether or not there is a relationship between stage of differentiation and Fo expression, we have analyzed the kinetics of Fo expression during the growth of cultured mouse bone marrow-derived macrophages (BMDM). BMDM were grown in serum free medium to avoid the possible influence of undefined serum factors. In this medium they could be maintained over a period of up to 20 days with cell yields comparable to those obtained with serum-supplemented media. Fo antigen was assayed with a specific antibody using both a whole cell ELISA and immunocytochemical staining of cells grown on slides. With increasing age in culture, BMDM showed a gradual quantitative increase in Fo expression and parallel increase in the Fo+ BMDM fraction from about 10% Fo+ cells on the 10th day of culture to a maximum of 50%-60% Fo+ cells between the 17th and 19th days. The temporal control over the development of the Fo+ cell fraction was intrinsic to BMDM maturation but was specific for Fo. During the same time period expression of MHC class II (Ia) remained consistently low, whereas expression of both Mac-1 (C3bR) and the macrophage-specific marker ER-BMDM-1 was always high. The interleukins IL-4 and especially IL-6 induced a premature expression of Fo at earlier stages of BMDM culture, but neither could promote further Fo expression once the intrinsically occurring maximum had been reached. No evidence in support of an autocrine regulation of Fo expression by IL-6 could be obtained, nor could a connection between cell cycle status and Fo expression be established. These data provide further evidence that Fo is a temporally regulated differentiation marker for a mouse macrophage subpopulation and for modulation of its expression by lymphokines.

Modulation of Forssman glycosphingolipid expression by murine macrophages: coinduction with class II MHC antigen by the lymphokines IL4 and IL6

In contrast to murine spleen M phi, resident peritoneal M phi from health mice express very little Forssman glycolipid antigen (Fo). The following experiments suggest that Fo expression by peritoneal M phi may be associated with inflammation. Balb/c and CBA/J mice were given inflammatory stimuli by i.p. injection of live BCG, thioglycollate (TG), Corynebacterium parvum (CP), proteose peptone (PP), or LPS. Control animals received pyrogen-free saline. Expression of Fo and Ia antigen by peritoneal M phi was determined by immunofluorescence after 4 d. Application of TG or CP led to an up to 30-fold increase in Fo+, Ia+ double positive M phi over that in control animals. LPS caused mainly an increase in the percentage of double-positive M phi, whereas no effects were seen in BCG or PP treated animals. To clarify the possible involvement of cytokines in this process and to identify these, the effects of LPS and various cytokines on in vitro induction of Fo and Ia expression were studied in further experiments. LPS, IL6, and IL4 caused induction of up to 15% Fo+ and Ia+ M phi after a 4 d culture period. M phi colony stimulating factor (M-CSF) from lung-conditioned medium was also moderately active. IL1, TNF, and IL2 had no influence, whereas IFN-gamma only induced Ia. For a successful in vitro induction of Fo and Ia, a prior priming of the mice with PP appeared mandatory. This suggests that only M phi of a certain developmental stage can acquire Fo under the influence of the appropriate cytokines. The data may provide the first evidence for cytokine-mediated modulation of a glycolipid antigen of known chemical structure.