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Direct activation of guinea pig macrophages by a B-cell mitogen
Abstract:
Since polyclonal B-cell activators (PBA) require macrophages to induce modifications in the lymphocyte in vitro primary response to thymus-dependent antigens, we have investigated whether PBA act directly on macrophages. [14C]glucosamine uptake by guinea pig peritoneal adherent cells after stimulation with purified protein derivative (PPD), lipopolysaccharide (LPS), and dextran sulfate (DxS) was tested. PPD produced an increased [14C]glucosamine uptake, whereas LPS and DxS did not. According to our experiments, (a) PPD does not require the presence of lymphocytes to stimulate macrophages; furthermore, when lymphocytes were present in a concentration higher than 5%, a suppressor effect in the glucosamine uptake was found, and (b) there was no significant difference between the findings when peritoneal adherent cells were cultured in normal medium and in supernatant of lymphocyte cultures stimulated with PPD.
Insights
Polyclonal B-cell activators (PBA) were investigated for direct effects on macrophages. Purified protein derivative (PPD) stimulated macrophage activity, unlike LPS or dextran sulfate, indicating PBA can act directly on macrophages.
Area of Science:
- Immunology
- Cell Biology
Background:
- Polyclonal B-cell activators (PBA) are known to require macrophages for lymphocyte activation.
- The direct effect of PBA on macrophages remains unclear.
Purpose of the Study:
- To investigate if polyclonal B-cell activators (PBA) directly stimulate macrophages.
- To determine the effect of purified protein derivative (PPD), lipopolysaccharide (LPS), and dextran sulfate (DxS) on macrophage activity.
Main Methods:
- Guinea pig peritoneal adherent cells were isolated.
- [14C]glucosamine uptake was measured after stimulation with PPD, LPS, and DxS.
- The influence of lymphocytes on macrophage stimulation was assessed.
Main Results:
- PPD significantly increased [14C]glucosamine uptake in macrophages.
- LPS and DxS did not affect [14C]glucosamine uptake.
- PPD stimulated macrophages independently of lymphocytes, with lymphocyte presence above 5% showing a suppressive effect.
Conclusions:
- PBA, specifically PPD, can directly activate macrophages.
- Lymphocytes may modulate the direct activation of macrophages by PPD.
- Macrophage activation by PPD is not dependent on lymphocyte-derived factors in supernatants.