B1-derived, long-lived IgM plasma cells persist in the spleen and confer long-term protection Open Access

Bohannon, Caitlin Darcy (2016)

Permanent URL: https://etd.library.emory.edu/concern/etds/5712m7288?locale=en


Long-lasting protection is a hallmark of the adaptive immune response, and long- lived plasma cells have the capacity to produce neutralizing antibodies for as long as a lifetime. These antigen-specific, long-lived IgG plasma cells develop following exposure to antigen, along with T cell help. This T cell interaction leads to the formation of germinal centers, where activated B cells undergo class- switching and affinity maturation to generate high-affinity, long-lived IgG plasma cells and memory B cells. Here we describe an alternative pathway of plasma cell development that can occur in the absence of germinal centers, in which plasma cells are not class- switched but are somatically mutated. These activation induced cytidine deaminase-induced (AID) mutations are less frequent than in IgG plasma cells, and surprisingly they are observed within the antibody framework rather than within the antigen-binding regions (CDRs). The resulting IgM plasma cells are likely of mixed affinity, compared to the clonally selected, high-affinity IgG plasma cells. The long-lived IgM plasma cells originate from the B1 compartment, and are distinct from natural IgM cells. Unlike long-lived IgG plasma cells, which are resident in the bone marrow, IgM plasma cells persist within the red pulp of the spleen. They develop early in the immune response - prior to germinal center formation and the development of long-lived IgG plasma cells. Further, IgM plasma cells alone are sufficient to protect against viral challenge, even in the absence of IgG and memory B and T cells. Finally, we discuss the evolution and functionality of this long-lived IgM pathway, and the potential significance of these IgM plasma cells to rational vaccine design.

Table of Contents



Chapter 1: Introduction 1

The B cell repertoire 1

B cell activation and differentiation 3

Figure 1: Model of B cell differentiation 4

Figure 2: High frequency of mutations in CDRs following antigen-selection 10

B cell trafficking and survival 10

B1 B cells 14

The evolution of humoral immunity 17

B cells in clinical disease 18

The importance of antibody response in vaccine design 22

Summary 23

Literature Cited 24

Chapter 2: Long-lived, antigen-induced IgM plasma cells demonstrate somatic mutations and contribute to long-term protection 36

Figure 1: Expanded populations of IgM plasma cells persist in the spleen in response to diverse immunogens and pathogens 65

Figure 2: Antigen-specific, long-lived IgM plasma cells persist post-adoptive transfer and preferentially localize in the spleen, IgG plasma cells localize in the bone marrow 67

Figure 3: IgM plasma cells show evidence of somatic hypermutation, even when germinal centers are ablated 69

Figure 4: IgM heavy chain mutations are predominantly transitions and found in AID hotspot motifs, are AID-induced and AID-dependent 71

Figure 5: IgM heavy chain mutations are not enriched in CDR regions, unlike IgG, and show no evidence of antigen-selection 73

Figure 6: Germinal center independent IgM plasma cells are capable of neutralizing influenza virus in vitro and protecting the animal against infection in vivo 74

Figure 7: IgM plasma cells are capable of protecting the animal against infection in vivo in the absence of IgG plasma cells, memory B cells, and T cell help 76

Supplementary Table 1: Total heavy chain sequences with >90% homology to IgHV 186.2 78

Supplementary Figure 1: Antigen-specific IgM and IgG titers persist, post-adoptive transfer of plasma cells into recipient Rag-/- mice 79

Supplementary Figure 2: Long-lived IgM, but not IgG, plasma cells are generated when germinal center formation is blocked by Cobra Venom Factor (CVF) treatment 80

Supplementary Figure 3: Treatment with anti CD4 and CD8 antibodies leads to efficient depletion of CD4 and CD8 T cell 81

Literature Cited 82

Chapter 3: B1b B cells give rise to long-lived IgM plasma cells early in immune response 86

Figure 1: Long-lived IgM plasma cells require early T cell help but not germinal center formation, arise early in immune response 104

Figure 2: Plasma cells localize to the red pulp of the spleen, and only bind NP22CGG in immunized mice 105

Figure 3: Differential expression of chemokine and survival receptors on the surface of IgG and IgM long-lived plasma cells 107

Figure 4: Figure 4: B1b, not B2, cells give rise to long-lived IgM plasma cells, even in the absence of germinal centers 109

Figure 5: Long-lived IgM arises early in immune response 111

Supplementary Figure 1: B1b B cells proliferate only modestly in response to stimulation when compared to B2 cells 112

Literature Cited 113

Chapter 4: Discussion 116

A new model of plasma cell development 116

Figure 1: Model of B1-derived and B2-derived plasma cell differentiation pathways 119

The role of long-lived IgM plasma cells 120

Potential for clinical applications 126

Future directions of this study 129

Literature Cited 131

About this Dissertation

Rights statement
  • Permission granted by the author to include this thesis or dissertation in this repository. All rights reserved by the author. Please contact the author for information regarding the reproduction and use of this thesis or dissertation.
  • English
Research Field
Committee Chair / Thesis Advisor
Committee Members
Last modified

Primary PDF

Supplemental Files