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Obligatory role of macrophages in dengue virus antigen presentation to B lymphocytes
N Rizvi1, U C Chaturvedi, A Mathur
1Postgraduate Department of Microbiology, K.G. Medical College, Lucknow, India.
Abstract:
The study was undertaken to investigate the role of dengue type 2 virus (DV)-infected mouse peritoneal macrophages (M phi) in presentation of the DV antigen to B lymphocytes as shown by counting virus-specific IgM antibody plaque-forming cells (PFC). It was observed that heat-killed or glutaraldehyde-fixed M phi did not present the antigen. Pretreatment of M phi with the lysosomotropic compounds ammonium chloride and chloroquine inhibited the antigen presentation. Depletion of M phi from the spleen cell cultures abrogated the immune response to DV. The tryptic-digested DV antigen could stimulate immune responses in B-lymphocyte enriched (depleted of M phi and T cells) spleen cell cultures, and the digested antigen could be presented by glutaraldehyde-fixed M phi. Pretreatment of M phi with a trypsin inhibitor abrogated antigen presentation. The findings thus show that even for presentation to B cells the DV antigen must be processed by M phi by a trypsin-like protease.
Insights
Macrophages process dengue type 2 virus (DV) antigens for B cell presentation. This involves a trypsin-like protease, as heat-killed or fixed cells, and lysosomotropic compounds inhibit the immune response.
Area of Science:
- Immunology
- Virology
- Cell Biology
Background:
- Macrophages (M phi) play a crucial role in initiating adaptive immune responses.
- Antigen presentation to B lymphocytes is essential for antibody production.
- The specific mechanisms of dengue virus (DV) antigen processing by M phi remain incompletely understood.
Purpose of the Study:
- To investigate the role of DV-infected mouse peritoneal macrophages in presenting DV antigen to B lymphocytes.
- To elucidate the processing requirements for DV antigen presentation by macrophages.
Main Methods:
- Utilized mouse peritoneal macrophages (M phi) infected with dengue type 2 virus (DV).
- Assessed antigen presentation by counting virus-specific IgM antibody plaque-forming cells (PFC).
- Employed heat-killed, glutaraldehyde-fixed M phi, lysosomotropic compounds (ammonium chloride, chloroquine), and enzymatic digestion (trypsin) to study antigen processing.
Main Results:
- Heat-killed or glutaraldehyde-fixed M phi failed to present DV antigen.
- Lysosomotropic compounds inhibited M phi-mediated antigen presentation.
- Tryptic-digested DV antigen stimulated immune responses and could be presented by fixed M phi, an effect abrogated by trypsin inhibitors.
Conclusions:
- Macrophages require processing of DV antigen via a trypsin-like protease for presentation to B cells.
- This processing step is critical for initiating an effective humoral immune response against dengue virus.