Generation and functional capacity of polyclonal alloantigen-specific memory CD4 T cells.

Alloreactive memory T cells can significantly impact graft survival due to their enhanced functional capacities, diverse tissue distribution and resistance to tolerance induction and depletional strategies. However, their role in allograft rejection is not well understood primarily due to the lack of suitable in vivo models. In this study, we use a novel approach to generate long-lived polyclonal alloreactive memory CD4 T cells from adoptive transfer of alloantigen-activated precursors into mouse hosts. We demonstrate that CD25 upregulation is a marker for precursors to alloantigen-specific memory and have created a new mouse model that features an expanded population of polyclonal alloreactive memory T cells that is distinguishable from the naive T-cell population. Furthermore, we show that alloreactive memory T cells exhibit rapid recall effector responses with predominant IFN-gamma and IL-2 production, and mediate vigorous allograft rejection. Interestingly, while we found a heterogeneous distribution of allomemory T cells in lymphoid and nonlymphoid tissues, they were all predominantly of the effector-memory (CD62Llo) phenotype. Our results present a unique model for the generation and tracking of polyclonal allospecific memory CD4 T cells in vivo and reveal insights into the distinct and robust nature of alloreactive T-cell memory.

Buspirone, a 5-HT(1A) receptor agonist, dilates the perfused rat uterine vascular bed through alpha(1)-adrenoceptor blockade.

In the perfused rat uterine vascular bed, 5-hydroxytryptamine (5-HT) produced dose-dependent vasoconstrictor responses. Buspirone, a selective 5-HT(1A) receptor agonist, was not effective at low doses but produced a response at high doses. When perfusion pressure was raised with phenylephrine, responses to 5-HT were enhanced while buspirone produced dose-dependent vasodilator responses. Buspirone did not produce vasodilation when perfusion pressure was raised with vasopressin or U46619. Buspirone-induced vasodilator responses were not affected by selective 5-HT(1A) receptor antagonists, 8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspiro[4,5]-decane-7,9-dione (BMY 7378) and N-tert-butyl-3-(4-[2-methoxyphenyl]piperazin-1-yl)-2-phenylpropanamide (WAY 100478), indicating that specific 5-HT(1A) receptors might not be involved in buspirone-induced vasodilation. Buspirone (3 x 10 (-5) M) and prazosin (3 x 10(-9) M) antagonized noradrenaline-induced constriction with dose ratios of 19.1+/-2.9 and 11.7+/-2.1, respectively. The dose ratio of these antagonists in combination was 46.6+/-8.1. Since the combination ratio is closer to the sum of their individual dose ratios less 2 (i.e. DR(p)+DR(b)-2) than it is to the product of their individual dose ratios, our data suggest an interaction of buspirone with alpha(1)-adrenoceptors. Buspirone also protected adrenoceptors against inactivation by phenoxybenzamine confirming that buspirone interacted with alpha(1)-adrenoceptors. We concluded that buspirone-induced vasodilation of the perfused rat uterine vascular bed is mediated through blockade of alpha(1)-adrenoceptors rather than through 5-HT(1A) receptors.

Heterogeneity of alpha 1-adrenoceptor subtypes mediating noradrenaline-induced contractions of the rat superior mesenteric artery.

The effects of subtype-selective alpha 1-adrenoceptor antagonists on noradrenaline-induced contractions of ring segments of rat superior mesenteric artery were investigated to determine the subtype(s) of alpha 1-adrenoceptors mediating contractions in this preparation. Noradrenaline-induced contractions of rat mesenteric artery ring segments were potently and surmountably antagonized by prazosin, WB 4101 and BMY 7378. Judging from the slopes of the Schild regression lines, which were significantly different from 1, WB 4101 and BMY 7378 behaved as noncompetitive antagonists. Spiperone and 5-methylurapidil were only effective at high concentrations. Chloroethylclonidine (CEC, 100 mumol/l) displaced the noradrenaline concentration-response curve to the right reducing its potency approximately 100-fold. Noradrenaline-induced contractions post-CEC were also antagonized by prazosin. However, prazosin was less potent against these contractions. A 61,603, a selective alpha 1A-adrenoceptor agonist, contracted ring segments of the mesenteric artery. These contractions were antagonized by prazosin, however with a low affinity, indicating interaction with a low-affinity receptor subtype. It was therefore concluded that alpha 1D- and, possibly, alpha 1L-adrenoceptor subtypes mediated noradrenaline- induced contractions of the rat superior mesenteric artery.