Tumour-necrosis factor from the rabbit. II. Production by monocytes.

Mononuclear cells from normal rabbit blood were cytotoxic to a number of cell lines in vitro. The cytotoxic cells were contained in the monocyte-enriched fraction adherent to plastic. Supernatants of the monocyte-enriched fraction had the same cytotoxic specificity as the parent cells. The cytotoxic factor precipitated in 50% saturated ammonium sulphate solution and on gel filtration was heterogeneous with a mol.-wt. range of 30--50,000 u. On the basis of specificity and molecular characteristics, this cytotoxic factor closely resembles rabbit tumour-necrosis factor (TNF) suggesting that TNF or a closely related factor is a normal product of mononuclear phagocytes.     

Uncoating of turnip yellow mosaic virus RNA in vivo

Following mechanical inoculation of leaves with turnip yellow mosaic virus (TYMV), a significant proportion of the retained inoculum is uncoated within 45 sec, and the process is more or less complete after 2 min. At least 80-90% of the uncoating takes place in the epidermis. The application of virus to the intact leaf is essential for uncoating to occur. The uncoating process is not confined to plants which are known hosts for TYMV. The process gives rise to empty shells and low molecular weight protein. The empty shells probably lose a pentamer or hexamer of protein when the RNA is released. On a per cell basis the number of virus particles uncoated can be very large-approximately 106 particles per cell. The data suggest that at high inoculum concentrations most of the released RNA is inactivated on or within the epidermis.