Related Experiment Video
Updated: Jul 3, 2026
Visualization of Streptococcus pneumoniae within Cardiac Microlesions and Subsequent Cardiac Remodeling
Published on: April 7, 2015
Macrophages pulsed with Streptococcus pneumoniae elicit a T cell-dependent antibody response upon transfer into naive
Sam Vasilevsky1, Jesus Colino, Roman Puliaev
1Department of Pathology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, USA.
Abstract:
Macrophages are less effective than DC at priming naive CD4(+) T cells, suggesting that DC are unique in initiating T cell-dependent Ab responses. We compared the ability of DC and macrophages, pulsed in vitro with Streptococcus pneumoniae, to elicit protein- and polysaccharide-specific Ig isotype production upon adoptive transfer into naive mice. S. pneumoniae-activated DC secreted more proinflammatory and anti-inflammatory cytokines, expressed higher levels of surface MHC class II and CD40, and presented S. pneumoniae or recombinant pneumococcal surface protein A (PspA) to a PspA-specific T hybridoma more efficiently than macrophages. However, upon adoptive transfer into naive mice, S. pneumoniae-pulsed macrophages elicited an IgM or IgG anti-PspA and anti-polysaccharide response comparable in serum titers and IgG isotype distribution to that induced by DC. The IgG anti-PspA response, in contrast to the IgG anti-polysaccharide, to S. pneumoniae-pulsed macrophages was T cell-dependent. S. pneumoniae-pulsed macrophages that were paraformaldehyde-fixed before transfer or lacking expression of MHC class II or CD40 were highly defective in eliciting an anti-PspA response, although the anti-polysaccharide response was largely unaffected. To our knowledge, these data are the first to indicate that macrophages can play an active role in the induction of a T cell-dependent humoral immune response in a naive host.
Insights
Macrophages can initiate T cell-dependent antibody responses, challenging the long-held belief that only dendritic cells (DCs) possess this unique capability. This study reveals macrophages
Area of Science:
- Immunology
- Cell Biology
Background:
- Dendritic cells (DCs) are traditionally considered unique in initiating T cell-dependent antibody (Ab) responses.
- Macrophages are generally viewed as less effective than DCs in priming naive CD4(+) T cells.
Purpose of the Study:
- To compare the capacity of DCs and macrophages to elicit T cell-dependent and T cell-independent humoral immune responses.
- To investigate the role of antigen presentation by macrophages in initiating adaptive immunity.
Main Methods:
- In vitro pulsing of DCs and macrophages with Streptococcus pneumoniae.
- Adoptive transfer of pulsed cells into naive mice.
- Analysis of anti-pneumococcal protein A (PspA) and polysaccharide-specific Ig isotype production.
- Assessment of T cell dependency by using paraformaldehyde-fixed or MHC class II/CD40-deficient macrophages.
Main Results:
- S. pneumoniae-pulsed macrophages induced IgM and IgG responses against PspA and polysaccharides comparable to DCs.
- The IgG anti-PspA response elicited by macrophages was T cell-dependent.
- Macrophage antigen presentation via MHC class II and CD40 was crucial for the T cell-dependent anti-PspA response, but not the anti-polysaccharide response.
Conclusions:
- Macrophages can actively induce T cell-dependent humoral immune responses in a naive host.
- This finding challenges the established view of DCs as the sole initiators of such responses.
- Macrophages play a significant role in initiating adaptive immunity, particularly T cell-dependent antibody production.
More Related Videos
12:21A Mouse Model for the Transition of Streptococcus pneumoniae from Colonizer to Pathogen upon Viral Co-Infection Recapitulates Age-Exacerbated Illness
Published on: September 28, 2022
09:12Characterization of Inflammatory Responses During Intranasal Colonization with Streptococcus pneumoniae
Published on: January 17, 2014
Related Concept Videos
01:31Defense Against Bacterial Pathogens
Phagocytes
Phagocytes are the frontline soldiers of the immune system. They include neutrophils and macrophages. Neutrophils are the most abundant type of white blood cell and are quickly mobilized to the site of infection. Macrophages are larger cells that patrol...
01:40Cell-mediated Immune Responses