Role of B cells as antigen-presenting cells in vivo revisited: antigen-specific B cells are essential for T cell expansion in lymph nodes and for systemic T cell responses to low antigen concentrations
A. Rivera et al., Role of B cells as antigen-presenting cells in vivo revisited: antigen-specific B cells are essential for T cell expansion in lymph nodes and for systemic T cell responses to low antigen concentrations, INT IMMUNOL, 13(12), 2001, pp. 1583-1593
Studies in B cell-deficient mice generated by continuous injection of anti-
mu antibodies (mu SM) showed that T cell priming in lymph nodes was depende
nt on antigen presentation by B cells. This concept has recently become con
troversial since a wide range, from complete deficiency to near normal T ce
ll responses, was reported in studies carried out with B cell-deficient mic
e generated by gene disruption (mu MT). In this study we show that in the a
bsence of B cells, T cell responses are greatly reduced in all the availabl
e mu MT mouse strains although responses in mu MT of the C57BL/6 background
(which were used for most studies with mu MT) were much more variable and
could reach up to 42% of control. In contrast, T cell responses in mu MT --
> F-1 bone marrow chimeras which have the same phenotype as mu MT were tota
lly impaired, suggesting a principle difference between mice developing wit
hout B cells (mu MT mice) and mu SM which are made B cell deficient only af
ter birth. Normal T cell priming was completely restored by reconstitution
of mu MT and mu MT --> F-1 mice with syngeneic B cells. Interestingly, only
B cell populations containing antigen-specific B cells were capable of rec
onstituting T cell responses. Monoclonal B cells taken from Ig transgenic m
ice could not reconstitute responses to an irrelevant antigen. We also foun
d that B cells were also required for systemic T cell priming when antigen
concentrations were limiting but were not required for priming (for T cell
help) when mice were immunized with a high antigen dose.