Editing B cell (section)

===T cell-independent activation===
{{Main|T independent antigen (TI)}}
Antigens that activate B cells without T cell help are known as [[T independent antigen (TI)|T cell-independent (TI) antigens]]<ref name=":0" /> and include foreign polysaccharides and unmethylated CpG DNA.<ref name=":8" /> They are named as such because they are able to induce a humoral response in organisms that lack T cells.<ref name=":0" /> B cell response to these antigens is rapid, though antibodies generated tend to have lower affinity and are less functionally versatile than those generated from T cell-dependent activation.<ref name=":0" />

As with TD antigens, B cells activated by TI antigens need additional signals to complete activation, but instead of receiving them from T cells, they are provided either by recognition and binding of a common microbial constituent to [[Toll-like receptor|toll-like receptors (TLRs)]] or by extensive crosslinking of BCRs to repeated epitopes on a bacterial cell.<ref name=":0" /> B cells activated by TI antigens go on to proliferate outside lymphoid follicles but still in SLOs (GCs do not form), possibly undergo immunoglobulin class switching, and differentiate into short-lived plasmablasts that produce early, weak antibodies mostly of class IgM, but also some populations of long-lived plasma cells.<ref name=":11">{{cite journal | vauthors = Bortnick A, Chernova I, Quinn WJ, Mugnier M, Cancro MP, Allman D | title = Long-lived bone marrow plasma cells are induced early in response to T cell-independent or T cell-dependent antigens | journal = Journal of Immunology | volume = 188 | issue = 11 | pages = 5389–5396 | date = June 2012 | pmid = 22529295 | pmc = 4341991 | doi = 10.4049/jimmunol.1102808 }}</ref>