The acquisition of encephalitogenicity after sensitized cells are conditioned with myelin basic protein or concanavalin A

When cells from rats immunized against neural antigens are incubated with myelin basic protein or concanavalin A, their ability to transfer experimental allergic encephalomyelitis (EAE) is greatly increased. Using the rapid, localized form of EAE, we have shown that the increased encephalitogenicity of these cells was not manifest, or not fully manifest, in 1 day after passive transfer. Expression of the increased encephalitogenic potency required a period of residence in the recipient animal and this period did not depend on the duration of incubation in vitro. Conditioned cells were fully capable of eliciting the neutrophilic form of EAE, which is consistent with the notion that the recipient's mononuclear cells were not essential for the expression of the encephalitogenic potential of conditioned donor cells.     

An ultrastructural study of epididymal mouse spermatozoa binding to zonae pellucidae in vitro: sequential relationship to the acrosome reaction

Mouse sperm bind to the zona pellucida of the egg prior to penetration of the zona and entry into the perivitelline space. The question then arises: when does the acrosome reaction occur relative to these processes? An ultrastructural study of mouse epididymal sperm bound to the surface of the zona and in the privitelline space was undertaken to clarify this point. Cumulus-free mouse eggs were inseminated in either a complete defined culture medium capable of supporting in vitro fertilization or in Tris/NaCl buffer containing Ca+2. Both media support sperm binding to the zona to the same extent; binding is complete in 15 minutes. Unbound sperm were removed by a step gradient density centrifugation to yield a preparation of eggs with sperm firmly bound. All sperm in the perivitelline space had undergone the acrosome reaction. Sperm bound at the surface of the zonae pellucidae of eggs recovered at ten minutes after insemination all had intact acrosomes. At 40 minutes after insemination, half of the sperm were intact; the other half were in the initial stages of the acrosome reaction. At 90 minutes after insemination, 12% of the sperm had undergone the full acrosome reaction and were starting to penetrate the zona; of the balance, half were in various stages of the acrosome reaction, while half were still intact. These findings support the hypothesis that the sequence of the early reactions leading to fertilization in the mouse is: intact sperm binding to zona; acrosome reaction at the zona surface; penetration of the zona.