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Interaction of Ia antigen-bearing polymorphonuclear leukocytes and murine splenocytes
Abstract:
Polymorphonuclear leukocytes (PMN) were induced in the peritoneum of a Balb/c mouse by ip injection of Fusobacterium nucleatum (FN) (greater than 95% PMN). A subpopulation of PMN harvested bore Ia surface antigens and stimulated a mixed lymphocyte reaction (MLR) when cultured with C57B1/6J splenocytes. The reaction was blocked by a short prior incubation of PMN with anti-Ia antibody or PMN cell depletion by the same antibody plus complement. The Ia antigen-bearing PMN were capable of antigenic modulation since incubation of PMN for 24 h rendered the cells incapable of stimulating an MLR. The Ia antigen-bearing PMN produced a soluble material that enhanced the phytohemagglutinin (PHA) response of murine splenocytes and the active material was a product of live cells since the supernatants contained no detectable lactate dehydrogenase activity. The data suggest that murine PMN subpopulations, defined by surface Ia antigen, can modulate mitogenic responses by production of an enhancing factor(s).
Insights
Certain polymorphonuclear leukocytes (PMN) express Ia antigens, modulating immune responses. These Ia-bearing PMN can enhance lymphocyte proliferation through secreted factors, suggesting a role in immune modulation.
Area of Science:
- Immunology
- Cell Biology
- Infectious Disease
Background:
- Polymorphonuclear leukocytes (PMN) are key immune cells, traditionally known for phagocytosis and inflammation.
- The role of PMN in adaptive immune responses, particularly antigen presentation and lymphocyte activation, is less understood.
- Ia surface antigens (MHC class II) are typically associated with antigen-presenting cells like macrophages and dendritic cells.
Purpose of the Study:
- To investigate whether a subpopulation of murine polymorphonuclear leukocytes (PMN) expresses Ia surface antigens.
- To determine if Ia-bearing PMN can stimulate a mixed lymphocyte reaction (MLR) and modulate immune responses.
- To identify the nature of soluble factors produced by Ia-bearing PMN that influence lymphocyte activity.
Main Methods:
- Induction of PMN in mouse peritoneum using Fusobacterium nucleatum (FN).
- Isolation and characterization of Ia antigen-bearing PMN subpopulations.
- Assessment of MLR stimulation by PMN and blocking effects of anti-Ia antibodies or complement-mediated depletion.
- Evaluation of antigenic modulation by incubating PMN.
- Analysis of soluble factors produced by PMN for their effect on phytohemagglutinin (PHA) response and lactate dehydrogenase (LDH) activity.
Main Results:
- A subpopulation of FN-induced murine PMN expressed Ia surface antigens.
- These Ia-bearing PMN stimulated a significant MLR with allogeneic splenocytes, which was blocked by anti-Ia antibody.
- Incubation of PMN led to antigenic modulation, rendering them incapable of stimulating MLR.
- Ia-bearing PMN produced a soluble factor that enhanced the PHA response of splenocytes; this factor was derived from live cells.
Conclusions:
- Murine PMN subpopulations expressing Ia surface antigens can stimulate T cell responses.
- These PMN exhibit antigenic modulation, impacting their stimulatory capacity.
- Ia-bearing PMN secrete soluble factors that enhance lymphocyte mitogenic responses, suggesting a role in modulating adaptive immunity.