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Porcine alveolar macrophages: poor accessory or effective suppressor cells for T-lymphocytes
S Basta1, C P Carrasco, S M Knoetig
1Institute of Virology and Immunoprophylaxis, Sensemattstrasse 293, CH-3147, Mittelhäusern, Switzerland.
Abstract:
Porcine Alv-Mphi from bronchoalveolar lavages were tested for their function in an in vitro foot-and-mouth disease virus (FMDV)-specific lymphoproliferative recall response. The Alv-Mphi were seen to be poor accessory cells when compared with peripheral blood monocytes. This poor capacity was evident despite an efficient expression of SLA-DR region antigens, and other co-stimulatory adhesion molecules. It was noted that Alv-Mphi secrete relatively little interleukin 1 (IL-1beta), with or without LPS induction, even though mRNA for the cytokine could be detected. In contrast, blood monocytes with their effective accessory activity were potent secretors of IL-1. Although this IL-1beta would be important with respect to the accessory capacity of monocytic cells, it was noted that the absence of bioactive IL-1 from the Alv-Mpi cultures was not solely responsible for their poor accessory function. In fact, the Alv-Mphi produced factors which not only inhibited IL-1 bioactivity, but were also responsible for a clear suppression of lymphoproliferation. This suppressor activity was dependent on the type of monocytic cell present in the culture, being more prominent when "scavenger" phagocytes were present. Thus, the major role of Alv-Mphi s not as an accessory cell akin to monocytes, but as both a scavenger cell, related to Mphi derived from monocytes in the absence of inflammatory signals, and an immunoregulatory cell.
Insights
Porcine alveolar macrophages (Alv-Mphi) showed poor accessory cell function in FMDV recall responses compared to blood monocytes. They secrete less IL-1beta and produce factors that suppress lymphoproliferation, indicating a distinct immunoregulatory role.
Area of Science:
- Immunology
- Veterinary Virology
Background:
- Alveolar macrophages (Alv-Mphi) play a role in lung immunity.
- Their function in specific viral recall responses is not fully understood.
- Porcine alveolar macrophages (Alv-Mphi) were investigated for their accessory cell capacity.
Purpose of the Study:
- To evaluate the in vitro function of porcine Alv-Mphi in a foot-and-mouth disease virus (FMDV)-specific lymphoproliferative recall response.
- To compare the accessory cell function of Alv-Mphi with peripheral blood monocytes.
- To elucidate the immunoregulatory mechanisms of Alv-Mphi.
Main Methods:
- Porcine Alv-Mphi and peripheral blood monocytes were isolated.
- Cells were tested for their accessory function in an in vitro FMDV-specific lymphoproliferative recall response.
- Interleukin-1 beta (IL-1beta) secretion and mRNA expression were analyzed.
- Suppressive factors produced by Alv-Mphi were investigated.
Main Results:
- Alv-Mphi exhibited poor accessory cell function compared to blood monocytes, despite expressing SLA-DR and co-stimulatory molecules.
- Alv-Mphi secreted significantly less IL-1beta than monocytes, even after LPS induction.
- Alv-Mphi produced factors that inhibited IL-1beta bioactivity and suppressed lymphoproliferation, particularly in the presence of "scavenger" phagocytes.
Conclusions:
- Porcine Alv-Mphi function primarily as scavenger and immunoregulatory cells, rather than accessory cells like monocytes.
- Their reduced IL-1beta secretion and production of suppressive factors define their distinct role in immune responses.
- Alv-Mphi contribute to immune regulation in the lung environment, especially in the absence of inflammatory signals.