title: Autocrine models of B-lymphocyte growth. I. Role of cell contact and soluble factors in T-independent B-cell responses.
abstract: The requirements for triggering human B cells to DNA synthesis by T-independent polyclonal activators were examined. Optimal S phase entry of purified resting B cells infected with Epstein-Barr virus (EBV) or confronted with killed particles of Staphylococcus aureus Cowan Strain I (SAC) required a high density of cells in culture. Experiments varying culture vessel geometry and culture volumes revealed that the initial limiting quantity was a soluble activity generated in the B-cell cultures. A parallel observation was noted in the requirements for the sustained growth of EBV-transformed lymphoblasts. Autostimulatory soluble factors harvested from such cultures were able to augment DNA synthesis in low density cultures of resting cells triggered by EBV or SAC. Below a critical cell number, however, soluble factors by themselves, were not sufficient either for supporting primary B-cell responses or for maintaining the proliferation of transformed lymphoblasts. By employing conditions which encouraged cell contact it was found that a second, non-harvestable factor requiring cell proximity for its action was also necessary to promote B-cell growth. The implications of these findings for autocrine and paracrine models of B-cell activation are discussed.
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology* / Q000378:metabolism; D002450:Cell Communication; D002460:Cell Line; D002472:Cell Transformation, Viral; D004247:DNA / Q000096:biosynthesis; D006133:Growth Substances / Q000378:metabolism*; D004854:Herpesvirus 4, Human; D006801:Humans; D015847:Interleukin-4; D007958:Leukocyte Count; D008213:Lymphocyte Activation; D008222:Lymphokines / Q000378:metabolism*; D008938:Mitosis; D012995:Solubility; D013211:Staphylococcus aureus
chemical_list: D006133:Growth Substances; D008222:Lymphokines; D015847:Interleukin-4; D004247:DNA