Consistent with this, mice in which the transmembrane see more and/or cytoplasmic domains of membrane IgE are modified have altered primary and memory IgE responses [6 and 7]. The pathway of B cell differentiation to IgE production, including the location and lifespan of IgE-producing plasma cells and the identity of the memory B cells that give rise to IgE memory responses, has been poorly understood due to difficulties in identifying IgE-switched B cells in vivo [ 8, 9,
10• and 11•]. Recently, three separate groups have generated IgE reporter mice in which a fluorescent protein is associated with either transcription (M1 prime GFP knockin mice [ 12, 13, 14••, 15 and 16] and CɛGFP mice [ 17••]) or translation (Verigem mice [ 18••]) of the membrane IgE BCR ( Figure 1b). Studies utilizing these reporter mice, as well as earlier studies that utilized mice with monoclonal T and B cells [ 19], have greatly
increased the understanding of IgE production and memory and have revealed several mechanisms that limit IgE responses in vivo [ 10• and 11•]. IgE antibody responses in mice are typically selleck chemicals llc transient and are not sustained like IgG1 antibody responses [20 and 21]. Studies of Verigem mice revealed that early IgE responses are generated from short-lived IgE plasma cells located in extrafollicular foci. Late IgE responses arise from germinal centers, but in contrast to IgG1 germinal center B cells, which are sustained over time and which
give rise to long-lived IgG1 plasma cells, IgE germinal center B cells do not persist and are predisposed to differentiate into short-lived IgE plasma cells [18••]. Studies of M1 prime GFP knockin mice [14•• and 15] and CɛGFP mice [17••] also demonstrated a transient IgE germinal center response and the generation of primarily short-lived IgE plasma cells, although the studies of CɛGFP mice suggested that IgE germinal center B cells are predisposed to undergo apoptosis as opposed to differentiate into plasma cells. Thus, the persistence of IgE production in mice is limited by a transient germinal center response and a short lifespan of IgE-producing plasma cells. Although Molecular motor most IgE plasma cells produced in mice are short-lived cells that reside in the lymph nodes and spleen, a small number of IgE plasma cells were found in the bone marrow in Verigem mice, M1 prime GFP knockin mice, and CɛGFP mice [14••, 17•• and 18••]. These cells are likely to be long-lived IgE plasma cells that contribute to low levels of sustained IgE antibody production, consistent with other studies that have identified long-lived IgE plasma cells in the bone marrow of wildtype mice [22 and 23]. Very little is known about the memory B cells that give rise to IgE memory responses.