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Macrophage-lymphocyte interactions mediated by soluble factors
Abstract:
Adherent-cell-depleted primed rabbit splenocytes were capable of mounting an in vitro response to SRBC. The addition of alveolar macrophages (AM) to adherent-cell-depleted or unseparated lymphoid cell populations resulted in significant suppression of the PFC response. Suppressive activity was limited to AM and dependent on the presence of a ratio of 1 AM:20 lymphocytes. The cell-mediating suppression was found to be resistant to irradiation and antithymus globulin but sensitive to heat, freeze-thawing, and treatment with iodoacetamide. Suppression was mediated by a soluble factor (MW greater than 10,000 daltons) that required an AM-lymphocyte interaction for its production. Suppression appeared to be achieved through the inhibition of proliferation of antigen sensitive cells although the effect of AM could possibly be exerted on an early event in the immune response. AM were capable of enhancing the proliferative responses of rabbit lymphoid cells to PHA and Con A. Enhancing and suppressing activities of AM were abolished by inhibition of RNA synthesis but unaffected by inhibitors of DNA and protein synthesis.
Insights
Rabbit alveolar macrophages (AM) suppress antibody-producing cell responses but enhance responses to mitogens. This dual activity is mediated by a soluble factor dependent on RNA synthesis, impacting lymphocyte proliferation.
Area of Science:
- Immunology
- Cell Biology
- Macrophage Function
Background:
- Splenocytes are crucial for mounting immune responses.
- Alveolar macrophages (AM) play a role in lung immunity.
- The immunomodulatory functions of AM require further elucidation.
Purpose of the Study:
- To investigate the effect of rabbit alveolar macrophages (AM) on splenocyte immune responses.
- To characterize the suppressive and enhancing activities of AM.
- To identify the mechanisms underlying AM-mediated immunomodulation.
Main Methods:
- In vitro culture of primed rabbit splenocytes.
- Addition of alveolar macrophages (AM) to lymphocyte populations.
- Assessment of plaque-forming cell (PFC) response to SRBC.
- Analysis of lymphocyte proliferation in response to mitogens (PHA, Con A).
- Characterization of suppressive factors (irradiation, heat, chemical treatments).
Main Results:
- Alveolar macrophages (AM) significantly suppressed the PFC response in a dose-dependent manner (1 AM:20 lymphocytes).
- Suppressive activity was mediated by a soluble factor (>10,000 MW) requiring AM-lymphocyte interaction and RNA synthesis.
- AM enhanced lymphocyte proliferation to PHA and Con A, also dependent on RNA synthesis.
Conclusions:
- Rabbit alveolar macrophages (AM) possess both suppressive and enhancing immunomodulatory functions.
- Suppression of antibody response and enhancement of mitogen response are linked to RNA synthesis.
- AM influence antigen-sensitive cell proliferation and early immune events.