Cross‐linking of the surface immunoglobulin on lymphocytes from the bursa of Fabricius results in second messenger generation

Abstract

Much remains to be clarified the functional capacities of the two major reciprocal subsets of human CD4+ cells which we interpret to be naive and memory cells. CD4+ naive (CD45RA+, LFA-3-) and memory (CD45R0+, LFA-3+) cells were rigorously purified by immunomagnetic negative selection. Their proliferation was measured in response to four protocols of receptor-mediated activation: soluble anti-CD3 mAb, plastic-immobilized anti-CD3 mAb, activating pairs of anti-CD2 mAb, and "superantigens" staphyloccocal enterotoxins A and B (SEA and SEB). Naive cells proliferated much less than memory cells to each of these four regimens although their capacity to respond was demonstrated by strong PHA-induced proliferation. Although three of the regimens depend on autologous monocytes, poorer naive cell responses are also observed to anti-CD3 mAb immobilized on plastic in the absence of monocytes; this implies an intrinsic hyporesponsiveness of naive cells, independent of their potentially weaker interaction with monocytes. Naive cells proliferated less than memory cells to superantigens SEA and SEB over a wide dose range; this assumes particular importance because such superantigens are believed to more closely mimic antigen-specific stimulation than anti-CD3 mAb. The possibility was explored that hyporesponsiveness of naive cells reflects the fact that naive cells require additional co-stimuli to facilitate their activation. In support of this concept, we observed that proliferation of naive cells to anti-CD3 mAb and SEA or SEB (but not to anti-CD2 mAb pairs) was consistently enhanced by pre-activation of monocytes present in the culture. Naive cell proliferative responses were augmented further in cultures supplemented with interleukin (IL) 1 beta and IL 6 or exposed to the co-stimulating mAb anti-CD28 and anti-CD44. The pattern of augmentation was dependent on the specific triggering regimen: anti-CD44 mAb was particularly effective in augmenting the response to superantigens, anti-CD28 mAb for the anti-CD3 response and IL 1 beta/IL 6 for that induced by anti-CD2 mAb pairs. With particular combinations of stimulus/co-stimuli naive cell proliferation was as strong as that of memory cells. We interpret these findings to indicate that naive cells are capable of responding to antigen, but that such responses are critically dependent on the available co-stimuli in vivo.

Development of B cells expressing surface immunoglobulin molecules that lack V(D)J-encoded determinants in the avian embryo bursa of Fabricius

“…The transmembrane and cytoplasmic domains of chicken sIgM show extensive homology to their mammalian counterparts, and evolutionary conservation of signal transduction pathways through the sIgM complex (40)(41)(42) predict the existence of a chicken homologue to the mammalian Ig␣͞␤ heterodimer (43)(44)(45). If there is an extracellular ligand for the sIgM complex on bursal B cells, this ligand must recognize either the T chain (C2-C4 domains) or the extracellular domains of the predicted Ig␣͞␤ heterodimer.…”

Perinatal Deletion of B Cells Expressing Surface Ig Molecules That Lack V(D)J-Encoded Determinants in the Bursa of Fabricius Is Not Due to Intrafollicular Competition

“…Taken Surface expression of either endogenous sIgM or T is required for B cell expansion in the embryo bursa. Because the chicken sIgM complex includes homologues to CD79a (Ig␣) and CD79b (Ig␤), and both endogenous sIg and T (50,51) can transduce signals across the plasma membrane, constitutive basal signaling through the sIg complex may be sufficient to support B cell development in the embryo. This is analogous to the requirement for continuous sIg expression in the murine spleen, where B cell survival depends on constitutive basal signaling through sIg (52).…”

Ligation of Surface Ig by Gut-Derived Antigen Positively Selects Chicken Bursal and Peripheral B Cells

“…Changes in cytosolic calcium concentrations following receptor ligation were detected in INDO-1 (Molecular Probes, Eugene, OR)-loaded cells, as described (26). Briefly, cells were washed with IMDM growth media and loaded with 10 mM final concentration of INDO-1 at 37˚C for 45 min in the dark, and 1 3 10 6 loaded cells were transferred to tubes.…”

“…Samples were assayed on a BD LSR II and analyzed by BD FACSDiva software (BD Biosciences). Calcium mobilization was assessed following exposure of cells to anti-chicken H chain (HY18) or PE (26).…”