TLR7- and TLR9-Responsive Human B Cells Share Phenotypic and Genetic Characteristics

Abstract

B cells activated by nucleic-acid sensing Toll-like receptor 7 and TLR9 proliferate and secrete immune globulins. Memory B cells are presumably more responsive due to higher TLR expression levels, but selectivity and differential outcomes remain largely unknown. In this study, peripheral blood human B cells were stimulated by TLR7 or TLR9 ligands, with or without IFNα, and compared to activators CD40L plus IL-21, to identify differentially responsive cell populations, defined phenotypically and by BCR characteristics. While all activators induced differentiation and antibody secretion, TLR stimulation expanded IgM+ memory and plasma cell lineage committed populations and favored secretion of IgM, unlike CD40L/IL-21 which drove IgM and IgG more evenly. Patterns of proliferation similarly differed, with CD40L/IL-21 inducing proliferation of most memory and naïve B cells, in contrast to TLRs which induced robust proliferation in a subset of these cells. On deep sequencing of the IgH locus, TLR responsive B cells shared patterns of IgHV and IgHJ usage, clustering apart from CD40L/IL-21 and control conditions. TLR activators, but not CD40L/IL-21, similarly promoted increased sharing of CDR3 sequences. TLR responsive B cells were characterized by more somatic hypermutation, shorter CDR3 segments, and less negative charges. TLR activation also induced long positively charged CDR3 segments, suggestive of autoreactive antibodies. Testing this, culture supernatants from TLR stimulated B cells were found to bind HEp-2 cells, while those from CD40L/IL-21 stimulated cells did not. Human B cells possess selective sensitivity to TLR stimulation, with distinctive phenotypic and genetic signatures.

Inhibition of B‐cell activation and antibody production by triggering inhibitory signals via the PD‐1/PD‐ligand pathway

“…C). Together, these data are in line with observations of other groups showing that TLR9 (CpG‐B) stimulation mainly expands CD27 + IgM memory B cells …”

“…In cultures stimulated with CpG‐B, we observed a general increase in the frequency of CD27 + B cells and the occurrence of cells expressing high levels of CD27. This population is regarded to represent cells committed to the plasma cell lineage . Proliferation (dilution of the dye PKH26) was observed in CD27 low cells, but was particularly pronounced in CD27 high cells.…”

Dermatophagoides pteronyssinus group 2 allergen bound to 8-OH modified adenine reduces the Th2-mediated airway inflammation without inducing a Th17 response and autoimmunity

“…In addition, it has been shown that a TLR7 polymorphism is highly associated with human SLE (Wang et al, 2014;Tian et al, 2012). However, our previous and current data indicate that the conjugate did not show any ability to induce in vitro proliferation of human or murine B cells, while to the contrary other endosomal TLR7 or TLR9 ligands such as imidazoquinolines or CpG-ODNs did (Simchoni and Cunningham-Rundles, 2015). It is generally agreed that molecular structure, local amount, affinity for the receptors and time of the interaction may affect the quality and intensity of signals exerted by different ligands of the same TLR agonists: this could explain potential differences between the effects of modified adenines and other TLR7 ligands (Chang, 2010).…”

Adjuvanting an inactivated influenza vaccine with conjugated R848 improves the level of antibody present at 6 months in a nonhuman primate neonate model

“…TLR7 stimulation was associated with increased expression of Blimp-1, the master regulator of ASC differentiation as well as AID, the enzyme required for class switching and somatic hypermutation [23]. Studies using human B cells similarly reported a role for TLR7 in promoting differentiation into ASC [24, 25]. If R848 is promoting differentiation into ASC, it does not appear to be at the expense of memory B cell generation.…”