Identification of a novel receptor for B lymphocyte stimulator that is mutated in a mouse strain with severe B cell deficiency.

BLyS (also called BAFF, TALL-1, THANK, and zTNF4), a TNF superfamily member, binds two receptors, TACI and BCMA, and regulates humoral immune responses [1-7]. These two receptors also bind APRIL [7-10], another TNF superfamily member. The results from TACI(-/-) and BCMA(-/-) mice suggest the existence of additional receptor(s) for BLyS. The TACI knockout gives the paradoxical result of B cells being hyperresponsive, suggesting an inhibitory role for this receptor [11, 12], while BCMA null mice have no discernable phenotype [13]. Here we report the identification of a third BLyS receptor (BR3; BLyS receptor 3). This receptor is unique in that, in contrast to TACI and BCMA, BR3 only binds BLyS. Treatment of antigen-challenged mice with BR3-Fc inhibited antibody production, indicating an essential role for BLyS, but not APRIL, in this response. A critical role for BR3 in B cell ontogeny is underscored by our data showing that the BR3 gene had been inactivated by a discrete, approximately 4.7 kb gene insertion event that disrupted the 3' end of the BR3 gene in A/WySnJ mice, which lack peripheral B cells.

Competition for BLyS-mediated signaling through Bcmd/BR3 regulates peripheral B lymphocyte numbers.

Striking cell losses occur during late B lymphocyte maturation, reflecting BcR-mediated selection coupled with requisites for viability promoting signals. How selection and survival cues are integrated remains unclear, but a key role for B lymphocyte stimulator (BLyS(TM); trademark of Human Genome Sciences, Inc.) is suggested by its marked effects on B cell numbers and autoantibody formation as well as the B lineage-specific expression of BLyS receptors. Our analyses of the B cell-deficient A/WySnJ mouse have established Bcmd as a gene controlling follicular B cell life span, and recent reports show Bcmd encodes a novel BLyS receptor. Here we show that A/WySnJ B cells are unresponsive to BLyS, affording interrogation of how Bcmd influences B cell homeostasis. Mixed marrow chimeras indicate A/WySnJ peripheral B cells compete poorly for peripheral survival. Moreover, in vivo BrdU labeling shows that (A/WySnJ x BALB/c)F(1) B cells have an intermediate but uniform life span, indicating viability requires continuous signaling via this pathway. Together, these findings establish the BLyS/Bcmd pathway as a dominant mediator of B cell survival, suggesting competition for BLyS/Bcmd signals regulates follicular B cell numbers.

Ultrastructural changes in adrenaline- and SGC-cells after morphine coincide with alterations of adrenaline and dopamine levels.

The effects of morphine on chromaffin cell ultrastructure and catecholamine contents were studied using the adrenal glands from male mice (ICR strain). After 2 h adrenaline was increased 25% from 8.1 to 11.6 mumol/g tissue, followed by a 50% decrease to 5.2 mumol/g between 8-24 h and low values persisting at 72 h. Dopamine increased initially, reaching peak values of 0.5 mumol/g between 8-24 h, but had returned towards control values of 0.29 mumol/g by 72 h. Noradrenaline remained unchanged at 2.5 mumol/gram. Naloxone prevented alterations in adrenaline and dopamine levels. Ultrastructural examination revealed several types of catecholamine-storing cells. Of these the adrenaline and small-granule chromaffin (SGC) cells were more affected by morphine than noradrenaline cells. While the initial elevation of adrenaline 2 h after morphine was not accompanied by significant ultrastructural changes, the decrease after 8 and 24 h was paralleled by a significant (p less than 0.001) loss of adrenaline granules. Signs of active membrane turnover included an increase in the number of vacuoles, and the appearance of numerous coated omega profiles and coated (77.7 +/- 0.6 nm) vesicles. Clusters of synaptic-like vesicles (59.8 +/- 8.2 nm), slightly larger than neuronal vesicles (45.4 +/- 6.4), increased in the SGC-cells. After 72 h, the chromaffin granules in adrenaline cells remained low in numbers and were heterogeneous in electron density. Many synaptic-like vesicles were aligned along the SGC-cell membranes where only few chromaffin granules (109.3 +/- 20 nm) remained. Thus, continuous morphine exposure for 8-72 h increases the turnover of storage granules in adrenaline and SGC-cells with less effect on the noradrenaline cells which maintain catecholamine levels as indicated by biochemical analysis.