Functional heterogeneity among peritoneal macrophages. II. Enzyme content of macrophage subpopulations.

Rabbit peritoneal exudate (PE) macrophages were separated into subpopulations on discontinuous density gradients of bovine serum albumin. Four such macrophage subpopulations, referred to as bands A, B, C, and D (from lightest to heaviest buoyant density), were examined for differences in enzyme content. With regard to three acid hydrolases—acid phosphatases, β-glucuronidase, and cathepsin D—cells in bands A and B had greater enzyme activity than cells in bands C and D. A similar distribution of activities was observed for acid p-nitrophenylphosphatase. Peroxidase activity was present only in band D. Lysozyme activity was greatest in band D cells and least in band A cells. Only small differences in cytochrome c oxidase activity were observed among the subpopulations. Arginase activity was found to be greater in cells from band A than cells in bands B, C, and D. Macrophage subpopulations derived from PE macrophages placed in tissue culture for 7 days and macrophage subpopulation cells cultured for 2 days showed differences in acid phosphatase content similar to those seen with freshly obtained subpopulations. These results extend previous work demonstrating heterogeneity among PE macrophages.     

Functional heterogeneity among peritoneal macrophages: III. No evidence for the role of arginase in the inhibition of tumor cell growth by supernatants from macrophages or macrophage subpopulation cultures

The adherent population of peritoneal exudate cells (PE) obtained from rats and mice was analyzed for arginase activity in order to determine whether this enzyme has a role in tumor-growth-inhibitory activity. Freshly obtained tumor-growth-inhibitory rat PE cells had little or no arginase activity compared to the high levels of enzyme activity of mouse PE cells. Even after culturing, rat PE cells contained arginase activity 10 times less than that observed with comparable numbers of cultured or noncultured mouse cells. Subpopulations of mouse and rat PE macrophages, analyzed for arginase activity, showed that the light-density populations from cultured rat PE cells and noncultured mouse PE cells expressed arginase activities greater than that seen with heavy-density cells. However, the light-density rat PE cells expressed significantly less arginase activity than did the mouse cells. In attempts to test whether the inability of tumor cells to grow in supernatants or dialyzed supernatants from PE macrophage cultures is due to an arginine depletion, 200 μg/ml of the amino acid was added to the supernatants. The tumor-growth-inhibitory activities of such supernatants, as well as those from supernatants from highly active light-density rat PE macrophage cultures, were not abrogated by the addition of arginine. There was no correlation between the high levels of arginase activity of light-density PE macrophages and their antitumor activity and no evidence that the tumor-growth-inhibitory activity of rat or mouse PE macrophages in the macrophage-tumor models we studied was due to an arginine depletion.     

Cellular interactions in lymphocyte proliferation: effect of syngeneic and xenogeneic macrophages.

Secondary cell-mediated responses to ectromelia virus infection were studied using an in vitro system. Lymphoid “responder” cells from mice which had recovered from intravenous primary infection at various times prior to sacrifice, were cultured with syngeneic, virus-infected macrophages or spleen cells as “stimulator” cells at 39 °C, a temperature which prevented the virus from exerting cytopathic effects against responder cells. This restrictive temperature and medium with 2-mercaptoethanol at 10^?4M often gave viable cell yields of more than 100% of the original responder cells over 4 days of culture. Preliminary experiments showed that spleen cells from primed mice, cultured with syngeneic, infected spleen cells from normal mice gave the most powerful secondary cytotoxic cell responses as measured by ⁵¹Cr release from virusinfected H-2-compatible target cells. The cytotoxic cells were sensitive to anti-θ and complement treatment and lysed H-2-compatible, virus-infected target cells much more efficiently than infected, allogeneic target cells, thus indicating that they were T cells. Some activity against uninfected H-2-compatible target cells was also generated, but this was largely independent of the presence of virus-induced antigen, (i.e. infected stimulator cells were unnecessary) and therefore seemed to be a consequence of the cultural conditions. Cold target competition showed that this activity was the responsibility of a T cell subset separate from the virus-specific cytotoxic T cells. The peak of cytotoxic activity against virus-infected targets occurred at 4 days of culture and DNA synthesis was maximal on day 3. The concentration of cytotoxic T cells at the peak was eight-fold higher than at the peak of the splenic primary response in vivo, Memory T cells (precursors of secondary cytotoxic T cells) appeared in spleen within 12–14 days of primary infection in vivo, reached a plateau at 5–6 weeks and persisted for at least 16 months. Spleen cells appeared partly refractory to secondary stimulation in vitro at 8–10 days post-priming. This did not seem to be due to cellular migration from spleen to lymph nodes or peritoneal cavity, but its cause was not determined. Primary responses in vitro were not detectable under conditions optimal for secondary responses, thus suggesting a major quantitative, or qualitative difference between virgin and memory T cells.     

Cellular immune response against tumor cells. I. In vitro immunization of allogeneic and syngeneic mouse spleen cell suspensions against DBA mastocytoma cells

Spleen cell populations stimulated in vitro with as few as 1000 tumor cells produce cytotoxic effector cells. Syngeneic as well as allogeneic spleen cells respond to DBA mastocytoma tumor cells. There is a significant cellular immune response to allogeneic tumor cells 72 hr after exposure to antigen. By contrast, the response of DBA spleen cells to DBA mastocytoma tumor cells is first detectable at 120 hr following exposure to antigen. C57BL/6 spleen cells immunized against DBA mastocytoma antigen kill both DBA mastocytoma tumor cells and normal cells from DBA animals. DBA spleen cells immunized against DBA mastocytoma antigen kill only the DBA mastocytoma tumor cells, and not normal cells from DBA animals.     

In vitro interactions of murine peritoneal macrophages and sarcoma cells. I. Promotion of tumor cells proliferation by macrophages

An ascites subline (AA) of the murine sarcoma MC1M grows in vivo in the peritoneal cavity but dies in vitro when cultured on glass or collagen. The viability of AA cells in vitro is not influenced in cocultures with fibroblast cell line L929, and is diminished in cocultures supplemented with macrophage culture supernatant or in cocultures with non-adherent peritoneal cells. However, AA cells proliferate in vitro on glass or collagen when cocultured with syngeneic, semisyngeneic, and allogeneic peritoneal macrophages. This was demonstrated by tritiated thymidine incorporation assay, by AA cell number counting, and by measuring AA cell protein content. Proliferation also occurs when AA cells are separated from the macrophage monolayer by millipore filters.     

IFN-gamma- and cell-to-cell contact-dependent cytotoxicity of allograft-induced macrophages against syngeneic tumor cells and cell lines: an application of allografting to cancer treatment.

In allogeneic tumor or skin transplantation, the rejection process that destroys the allogeneic cells leaves syngeneic cells intact by discrimination between self and nonself. Here, we examined whether the cells infiltrating into the allografts could be cytotoxic against syngeneic immortal cells in vitro and in vivo. The leukocytes (i.e., macrophages (Mphi; 55-65% of bulk infiltrates), granulocytes (20-25%), and lymphocytes (15-20%)) infiltrating into allografts, but not into autografts, in C57BL/6 mice were cytotoxic against syngeneic tumor cells and cell lines, whereas the cytotoxic activity was hardly induced in allografted, IFN-gamma-/- C57BL/6 mice. Among the leukocytes, Mphi were the major population of cytotoxic cells; and the cytotoxic activity appeared to be cell-to-cell contact dependent. When syngeneic tumor cells were s.c. injected into normal C57BL/6 mice simultaneously with the Mphi-rich population or allogeneic, but not syngeneic, fibroblastic cells, tumor growth was suppressed in a cell number-dependent manner, and tumor cells were rejected either with a Mphi:tumor ratio of about 30 or with an allograft:tumor ratio of approximately 200. In the case of IFN-gamma-/- C57BL/6 mice, however, the s.c. injection of the allograft simultaneously with tumor cells had no effect on the tumor growth. These results suggest that allograft or allograft-induced Mphi may be applicable for use in cancer treatment and that IFN-gamma induction by the allograft may be crucial for the treatment.     

Schizophyllan (SPG)-treated macrophages and anti-tumor activities against syngeneic and allogeneic tumor cells

Summary We tested anti-tumor activities of macrophages treated with a neutral polysaccharide, schizophyllan (SPG), against syngeneic and allogeneic tumor cell lines. SPG was a macrophage stimulant which was not mitogenic to lymphocytes. That made a sharp contrast with the data that Corynebacterium parvum, BCG, and muramyl dipeptide (MDF) were macrophage stimulants which had lymphocyte-activating properties. Treatment of SPG-treated PEC with Thy12 monoclonal antibody and guinea pig complement did not affect the capabilities of tumor-cell-growth suppression by the treated PEC. Thus, the effector cells were peritoneal adherent cells (macrophages morphologically) and effector-to-target contact seemed to be necessary for effective tumor-cell-growth inhibition, although contradictory data exist for this. Murine peritoneal adherent cells harvested 4 days after a single IP injection of SPG at a dose of 100 mg/kg body weight of mouse showed the most prominent cytostatic and cytotoxic activities against syngeneic and allogeneic tumor cells. The distribution of anti-tumor activity in macrophages of various sizes followed the same pattern as macrophages treated with C. Parvum, i.e., larger macrophages showed more remarkable anti-tumor activity. Crude nonadherent peritoneal cells incubated with SPG at a concentration of 10 g/ml, 100 g/ml, or 1 mg/ml did not secrete lymphokine that rendered macrophages cytotoxic, while ConA-treated nonadherent cells did so. Furthermore, spleen cells treated with SPG in vivo did not secrete macrophage-activating lymphokine in the presence of SPG. On the other hand, addition of 1 mg/ml of SPG-treated peritoneal adherent cells and bone-marrow-derived macrophages in vitro rendered them cytotoxic to a moderate degree. This implies that SPG may activate macrophages directly, allowing them to become cytotoxic in the peritoneal cavity. Lastly, SPG could induce production of II-1-like factor to a moderate degree. SPG, whose molecular structure is well elucidated, will provide us with a strong tool to analyze the mechanism of macrophage activation both in vitro and in vivo.Abbreviations PEC peritoneal exudate cells - SPG schizophyllan - LPS lipopolysaccharide - Con A concanavalin A - CGN carrageenan - B. M. bone marrow - FCS fetal calf serum - BCG bacille Calmétte Guérin - Il-1 interleukin 1 - PPD pure protein derivatives - MDP muramyl dipeptide - C. parvum Corynebacerium parvum Dr. Sugawara is a Research Fellow of the Alberta Heritage Foundation for Medical ResearchDr. Lee is a Research Associate of the National Cancer Institute of Canada     

Schizophyllan (SPG)-treated macrophages and anti-tumor activities against syngeneic and allogeneic tumor cells

We tested anti-tumor activities of macrophages treated with a neutral polysaccharide, schizophyllan (SPG), against syngeneic and allogeneic tumor cell lines. SPG was a macrophage stimulant which was not mitogenic to lymphocytes. That made a sharp contrast with the data that Corynebacterium parvum, BCG, and muramyl dipeptide (MDF) were macrophage stimulants which had lymphocyte-activating properties. Treatment of SPG-treated PEC with Thy12 monoclonal antibody and guinea pig complement did not affect the capabilities of tumor-cell-growth suppression by the treated PEC. Thus, the effector cells were peritoneal adherent cells (macrophages morphologically) and effector-to-target contact seemed to be necessary for effective tumor-cell-growth inhibition, although contradictory data exist for this. Murine peritoneal adherent cells harvested 4 days after a single IP injection of SPG at a dose of 100 mg/kg body weight of mouse showed the most prominent cytostatic and cytotoxic activities against syngeneic and allogeneic tumor cells. The distribution of anti-tumor activity in macrophages of various sizes followed the same pattern as macrophages treated with C. Parvum, i.e., larger macrophages showed more remarkable anti-tumor activity. Crude nonadherent peritoneal cells incubated with SPG at a concentration of 10 micrograms/ml, 100 micrograms/ml, or 1 mg/ml did not secrete lymphokine that rendered macrophages cytotoxic, while ConA-treated nonadherent cells did so. Furthermore, spleen cells treated with SPG in vivo did not secrete macrophage-activating lymphokine in the presence of SPG. On the other hand, addition of 1 mg/ml of SPG-treated peritoneal adherent cells and bone-marrow-derived macrophages in vitro rendered them cytotoxic to a moderate degree. This implies that SPG may activate macrophages directly, allowing them to become cytotoxic in the peritoneal cavity. Lastly, SPG could induce production of II-1-like factor to a moderate degree. SPG, whose molecular structure is well elucidated, will provide us with a strong tool to analyze the mechanism of macrophage activation both in vitro and in vivo.     

Macrophage heterogeneity in tumor resistance: Cytostatic and cytotoxic activity of corynebacterium parvum-activated and proteose peptone-elicited rat macrophages against Moloney sarcoma tumor cells

Peritoneal macrophages from proteose peptone and Corynebacterium parvum (CP)-treated Lewis and Brown Norway rats were separated into subpopulations by centrifugation on discontinuous gradients of Ficoll. Four macrophage subpopulations were prepared and tested for cytostatic and cytotoxic activity against syngeneic and allogeneic Moloney sarcoma tumor cells. Macrophages were cocultured with tumor cells for 48 hr, whereupon either the inhibition of [¹²⁵I]iododeoxyuridine uptake was measured (cytostasis) or the tumor monolayers were observed for cytotoxic effects. CP-Activated macrophages from heavy-density portions of the gradient (8–10% and 10%-pellet) were highly cytostatic and cytotoxic to both the syngeneic and allogeneic tumor cells while macrophages from the light-density portions (4–6 and 6–8% Ficoll bands) were not. Proteose peptone-stimulated macrophages from the heavy-density portions of the gradient were cytostatic but not cytotoxic to the tumor cells. The effector macrophages from the CP-activated pool were large, well-differentiated cells as determined by electron microscopic examinations and had enhanced phagocytic activity when contrasted with the noncytotoxic, less dense macrophages.     

Antibody production useful for cytotoxicity against mouse MM2 tumor cells by peritoneal macrophages.

We applied an antibody-dependent macrophage-mediated cytotoxicity (ADMC) test in order to analyze the effector mechanism of the host-mediated antitumor effects induced by OK-432. Adherent peritoneal exudate (PE) cells were obtained from each of high (C3H/He) and low (B10) responder mice treated with OK-432, and 51Cr-labeled MM2 tumor cells were used as target cells. The cytotoxic activity in vitro coincided well with the results obtained in in vivo antitumor experiments. When adherent PE cells from C3H/He mice reacted with anti-MM2 serum from B10 mice, the degree of ADMC was significantly lower than that obtained with the anti-MM2 serum from C3H/He mice. The removal of IgG1 from the anti-MM2 serum induced in B10 mice resulted in the enhancement of ADMC activity. Then mean level of IgG2 in each of anti-MM2 sera from C3H/He and B10 mice was higher than in normal serum, and the IgG1 level in the antiserum from B10 mice was also higher than that in the serum from normal B10 mice. The present work suggested that the active component(s) in anti-MM2 serum participating in ADMC was a specific antibody of the IgG2 subclass, and that the inhibiting factor(s) was the IgG1 subclass.     

Evidence for cytostatic T cell activity in the effector mechanism against syngeneic TMT mammary tumor cells in mice

The effector mechanism of immune spleen cells against syngeneic TMT mammary tumor cells was analyzed in vitro. C3H/He mice were first inoculated with TMT tumor cells, and then the tumors were x-irradiated with 2000 rad 1 wk after the inoculation. Spleen cells from these treated mice inhibited the growth of tumor cells in vitro when assessed by (3H)-TdR incorporation by tumor cells (cytostatic activity). The same spleen cells did not have any cytotoxic activity on TMT tumor cells detected by a 51Cr-release assay. The cytostatic activity was mediated by Lyt-1+23- T cells. The purified T cells alone could not inhibit the growth of tumor cells, but accessory cells were required for the induction of cytostatic T cell activity. The accessory cells were Ia-positive, macrophage-like adherent cells. Furthermore, both T cells and macrophages were also required for the inhibition of tumor growth even after the spleen cells were activated in vitro. These results suggest T cells and macrophages play an important role in the effector mechanism against TMT mammary tumor cells. The mechanism of cytostasis by T cells and macrophages was discussed from the standpoint of the cellular interaction.     

Tumoricidal activity of syngeneic macrophages from melanoma-bearing mice: Changes with progressive tumor growth

Summary Changes in the cytostatic and cytotoxic activity of macrophages from tumor-bearing (TBM) and control mice were studied in a murine model of malignant melanoma. Syngeneic macrophages from TBM were initially noncytotoxic, but became cytotoxic and achieved their maximum destructive ability after 14 days of tumor growth. With continued tumor growth these macrophages either lost or had reduced cytotoxic activity. In contrast, macrophages from the same melanoma-bearing animals were significantly cytostatic at an earlier stage of tumor growth, but with continued melanoma growth these macrophages were no more cytostatic than controls. Moreover, melanomas grew slowly during the time when macrophages were observed to be cytostatic but grew rapidly at those stages when macrophages had a reduced ability to inhibit melanoma DNA synthesis. When these effector cells became cytotoxic melanomas were growing rapidly and changes in cytotoxicity had little effect on tumor mass. Thus, macrophages do not completely suppress melanoma proliferation and, although exhibiting cytotoxicity they were relatively ineffective in controlling a large mass of tumor cells.     

Functional activity of mouse peritoneal macrophages contaminated with gram-positive bacteria

The analysis of the functional and enzymatic activity of mouse peritoneal macrophages contaminated with Staphylococcus aureus and Listeria monocytogenes virulent strains is presented. The low bactericidal and digestive activity of these cells with respect to the above-mentioned microorganisms was determined. In this study a decrease in the activity of plasmatic membrane enzymes (5'-nucleotidase and ATP-ase) of macrophages contaminated with S. aureus and L. monocytogenes was observed, which was indicative of the stimulation of phagocytes. A rise in the activity of the oxygen-dependent system of macrophages contaminated with S. aureus and L. monocytogenes was detected by means of the nitro blue tetrazolium test. At the same time a decrease in the intracellular content of nitrogen oxide end metabolites in macrophages was detected with a rise in content of nitrogen oxide in the supernatants.     

Alloantigen-induced cytotoxicity against syngeneic tumor cells: analysis at the clonal level

It has been shown that peritoneal exudate cells (PEC) from BALB/c mice immunized with minor histocompatibility antigens presented by DBA/2 or B10.D2 spleen cells are capable of lysing syngeneic YC8 tumor cells in a 4-hr 51Cr-release assay. In this study, we employed limiting dilution analysis to determine the frequency of CTL precursors (CTL-P) reactive against both the specific DBA/2 (or P815) target and the syngeneic tumor YC8. The mean frequency of anti-DBA/2 CTL-P in PEC from BALB/c mice immunized with DBA/2 was 1/302. Between one-third and one-fifth of limiting dilution microcultures that exhibited lytic activity against DBA/2 lymphoblasts (or P815) were also able to lyse YC8. No lysis of YC8 was observed in the absence of a parallel lysis on DBA/2 lymphoblasts or P815 target cells. T cell clones, derived by micromanipulation from microcultures selected for cytotoxic activity against YC8 and/or P815, maintained either the specific anti-allogeneic or the doubly reactive ( antiallogeneic plus anti-syngeneic tumor) phenotype. Fourteen clones (six specific and eight doubly reactive) were tested for cytotoxic activity on a panel of target cells with different haplotypes. All showed H-2-restricted specificity for minor histocompatibility antigens shared by DBA/2 and B10.D2. The restriction element for some of the clones mapped in the K region of the H-2 complex, whereas for other clones the restriction element mapped in the D region; both K- and D-restricted clones were able to lyse YC8. When the clones that exhibited lysis on YC8 were tested on two other BALB/c tumor targets, LSTRA, a Moloney virus induced lymphoma, and RL male-1, a radiation induced lymphoma, two of seven were found to lyse all three syngeneic tumor targets equally well, but not syngeneic BALB/c blasts. These clones were functionally categorized as conventional CTL because they were unable to proliferate when cultured with antigen in the absence of exogenous lymphokines, and were unable to produce lymphokine with IL 2 activity when stimulated by the appropriate splenocytes. When tested in vivo in a Winn assay, a strong anti-tumor activity against YC8 was exerted by the anti-DBA/2 clones DY4 -3 and DY16 -3. These clones lysed both YC8 and the immunizing target cells in vitro. No in vivo effect in neutralizing YC8 tumor growth was observed with clone D2-1, a clone that lysed DBA/2 targets but not YC8 in vitro.     

Synergistic antitumor activity of interleukin-2 and cimetidine against syngeneic murine tumor

Summary Cimetidine, an H2 histamine receptor antagonist, is a potent immunomodulating agent, which acts by inhibiting suppressor T lymphocyte function. The present work investigated the effect, if any, of cimetidine on interleukin-2 (IL-2)-induced natural killer (NK) and lymphokine-activated killer (LAK) cell activities, and on in vivo antitumor activity using syngeneic colon 26 adenocarcinoma as the model. Mimicking the clinical conditions, all in vitro experiments were evaluated with the splenocytes prepared from tumor-bearing BALB/c mice. Ten days after subcutaneous inoculation of tumor cells (5 × 10⁵), animals were treated intraperitoneally daily with phosphate-buffered saline (PBS), cimetidine (2 mg kg^–1 day^–1), IL-2 (300 000 IU/day), or cimetidine plus IL-2 for 7 consecutive days. The treatment of IL-2 plus cimetidine increased NK and LAK cell activities significantly and synergistically at the end of the treatment (i.e. on day 18) as well as 1 week after the treatment (i.e. on day 25), in comparison with those of the control groups (PBS, cimetidine alone, IL-2 alone). Also, in vivo antitumor activity, as analyzed by a Kaplan-Meier life table with the log-rank test, revealed a significantly prolonged survival in the group treated with IL-2 plus cimetidine compared to the control groups. Phenotyping performed on the murine splenocytes on day 18 indicated a significant reduction in Lyt2-positive cells in the cimetidine-treated group in comparison with the PBS group. A significant increase in asialo GM1-positive cells and IL-2-receptor-positive cells was detected in the group treated with IL-2 plus cimetidine in comparison with the PBS and IL-2 control groups. Therefore, this study indicates a synergistic enhancement of IL-2-induced NK and LAK cell activities in tumor-bearing hosts by cimetidine, a noncytotoxic inhibitor of suppressor T function, and a significantly prolonged survival of tumor-bearing animals treated by IL-2 plus cimetidine. It also suggests the clinical potential of combination therapy of IL-2 with cimetidine.     

Comparative immunogenicity of irradiated and nonirradiated syngeneic and xenogeneic tumor cells containing a common specific transplantation antigen]

The authors compared the immunogenic activity for Syrian hamsters of native and irradiated syngeneic and xenogeneic tumour cells bearing on their surface common and SV40-specific transplantational antigen. The results obtained showed syngeneic tumour cells to be more immunogenic for the recipient than the xenogeneic tumour cells containing an antigen of the same specificity. Irradiation renders tumour cells, including the xenogeneic ones, more immunogenic, this possibly being associated with the capacity of nonirradiated cells to escape from immune recognition through their ability to divide.     

Augmentation of killer activity of murine spleen cells against allogeneic and syngeneic tumor cells by inoculation of alloantigen in vivo

After C57BL/6 (B6) mice were inoculated with BALB/c spleen cells via tail vein, kinetics of cytotoxic activities in the B6 mice against sensitizing alloantigens (H-2d) and against syngeneic antigens were investigated using, as target cells, P815 mastocytoma cells (H-2d) and B16 melanoma cells (H-2b). Cytotoxic activity against P815 in the B6 spleen cells reached a peak 3 days after alloantigen inoculation, decreased drastically on day 5 and rose again thereafter. The profile of anti-B16 cytotoxic activity was similar to that of anti-P815 activity. The cytotoxic activity against P815 was inhibited partially by cold B16, but that against B16 was not inhibited by cold P815. Surface phenotype of cytotoxic cells against P815 was Lyt2+, Thy1+, Asialo GM1+ and that of cytotoxic cells against B16 was Lyt2-, Thy1+/-, and Asialo GM1+. The results indicate that inoculation of B6 mice with allogeneic BALB/c spleen cells induce two types of cytotoxic cells; one is similar to lymphokine-activated killer (LAK) cells and the other is activated natural killer cells.     

Studies on the recognition of xenogeneic cells by nonimmune macrophages. I. Destruction of chicken fibroblasts in vitro by murine macrophages.

Human cord blood lymphocytes were compared with adult lymphocytes with regard to proportions of cells with surface markers for surface immunoglobulin (Ig), receptors for C′3 and the Fc-portion of IgG, as well as two types of erythrocyte rosettes (rapid and late E-rosettes). A significant decrease (P < 0.02 ? 0.05) in both early and late E-rosettes was noted when cord cells were compared to adult lymphocytes. After 20 hr of incubation at 37 °C, proportions of cells bearing Fc receptors in cord blood samples showed striking increments (P < 0.001) when compared with adult lymphocytes. T cell enrichment studies and sequential depletion of cells bearing Fc receptors as well as E-rosette forming cells indicated that the precursors of cells generating Fc receptors in vitro did not arise from cells with Fc receptors or T cell markers.     

Characterization of guinea pig macrophages: I. Mobility and maturation of peritoneal cells following inflammatory stimuli

The wide spectrum of activities of macrophages may, in part, be a reflection of their different subpopulations. Sedimentation velocity was used in separate different guinea pig macrophage populations which were then compared in assays which measure some of the parameters of inflammatory responses. Normal resident, thioglycollate-induced exudates or cells elicited by ip injection of tuberculin into BCG-sensitized animals were studied. In thioglycollate exudates the small, possibly recently derived monocytes were most responsive to chemotactic agents whereas populations with high sedimentation velocity were more phagocytic, responsive to MIF and produced more LAF. By contrast, all macrophage populations or subpopulations from sensitized animals challenged with PPD were unresponsive to lymphocyte-derived chemotactic factor, endotoxin-activated serum, or to N-formyl-l-methionyl-l-phenylalanine in chemotaxis assays. In addition, macrophages from these animals did not migrate from capillary tubes in MIF assays. The lack of migration is presumably due to the action of MIF on these cells in vivo. Cells with low sedimentation velocity (predominantly lymphocytes), however, did migrate from capillary tubes. We conclude that small cells elicited by a nonspecific stimulus are probably attracted to the inflammatory site by chemotaxins and must subsequently enlarge or mature before they are able to respond to MIF, to be activated to produce LAF, or to exhibit extensive phagocytosis.