Cannabinoid Receptor 2 (CB2) Plays a Role in the Generation of Germinal Center and Memory B Cells, but Not in the Production of Antigen-Specific IgG and IgM, in Response to T-dependent Antigens

Sreemanti Basu,Avijit Ray,Bonnie N Dittel,Mauricio Martins Rodrigues

doi:10.1371/journal.pone.0067587

Sreemanti Basu, Avijit Ray + Show 2 more

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https://doi.org/10.1371/journal.pone.0067587

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Abstract

The cannabinoid receptor 2 (CB2) has been reported to modulate B cell functions including migration, proliferation and isotype class switching. Since these processes are required for the generation of the germinal center (GC) and antigen-specific plasma and memory cells following immunization with a T-dependent antigen, CB2 has the capacity to alter the quality and magnitude of T-dependent immune responses. To address this question, we immunized WT and CB2−/− mice with the T-dependent antigen 4-hydroxy-3-nitrophenylacetyl (NP)-chicken-gamma-globulin (CGG) and measured GC B cell formation and the generation of antigen-specific B cells and serum immunoglobulin (Ig). While there was a significant reduction in the number of splenic GC B cells in CB2−/− mice early in the response there was no detectable difference in the number of NP-specific IgM and IgG1 plasma cells. There was also no difference in NP-specific IgM and class switched IgG1 in the serum. In addition, we found no defect in the homing of plasma cells to the bone marrow (BM) and affinity maturation, although memory B cell cells in the spleen were reduced in CB2−/− mice. CB2-deficient mice also generated similar levels of antigen-specific IgM and IgG in the serum as WT following immunization with sheep red blood cells (sRBC). This study demonstrates that although CB2 plays a role in promoting GC and memory B cell formation/maintenance in the spleen, it is dispensable on all immune cell types required for the generation of antigen-specific IgM and IgG in T-dependent immune responses.

Highlights

The endocannabinoid system is gaining increasing recognition as an important endogenous system with an ability to fine-tune the magnitude of immune responses
28 post-immunization, the draining lymph nodes (LN) were collected and germinal center (GC) B cells were analyzed by flow cytometry (A) and NP-specific IgM and IgG1 secreting plasma cells were determined by ELISPOT (B, C, respectively). (A) The percentage of Fas+GL7+ GC B cells within the B220+ population is shown. (B, C) Frequencies of NP-specific IgM+ (B) and IgG1+ spots (C) per 106 LN cells are shown. (D, E) NP-specific IgM and IgG1 titers were measured from two-fold serially diluted serum (1/200 to 1/1600 for IgM and 1/10000 to 1/80000 for IgG1) from NP-CGG-immunized Wild type (WT) and CB22/2 mice on days 0, 7, 14, and 28 by ELISA
We recently reported that CB22/2 mice have a significant reduction in T-independent immune responses [9] and in an extension of those studies, here we determined whether cannabinoid receptor 2 (CB2) regulates T-dependent immune responses

Summary

Introduction

The endocannabinoid system is gaining increasing recognition as an important endogenous system with an ability to fine-tune the magnitude of immune responses. CB2-deficiency did not alter affinity maturation, and antigen-specific memory B cells were reduced, the magnitude of the secondary antibody response was unaffected in CB22/2 mice.

Results

Conclusion