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In this paper we present in detail the very rapid and sensitive Millipore filter assay technique for measuring tritiated thymidine incorporation during semiconservativé DNA synthesis in human peripheral blood leucocyte cultures. Leucocytes which have been incubated with tritiated thymidine are trapped on a Millipore filter which is then suitably washed and dried. The filter is then immersed in scintillation fluid in a double-vial apparatus designed to ensure a reproducible counting geometry. Alternatively, the filter and its radioactive contents can be combusted to tritiated water, the radioactivity of which is then determined in a homogeneous counting system. The parameters related to the Miilipore filter assay technique are presented, and its present uses and general applicability discussed. [ABSTRACT FROM AUTHOR]

Target cell killing by lymphocytes can be induced by appropriate antibody complexed to target cell antigens. In this paper it is shown that this form of lymphocyte mediated cytotoxicity is susceptible to inhibition by third party immune complexes which compete with target cell bound antibody for receptors for immunoglobulin on the cytotoxic lymphocytes. The physical state of the complexes is investigated in relation to their inhibitory efficiency. Evidence is presented to show that soluble complexes which exist in antigen-antibody equilibrium or slight antigen excess are the most effective inhibitors. No evidence could be obtained to support the hypothesis that soluble immune complexes can induce indiscriminate cytotoxic activity in lymphocytes. The biological significance of this effect is discussed in relation to chronic inflammatory diseases. [ABSTRACT FROM AUTHOR]

In a previous paper it had been shown that up to 40% of human peripheral lymphocytes will make rosettes with sheep red cells. In this study the inhibitory effect of antilymphocyte serum (ALS) and of certain other preparations on this rosette phenomenon is described. ALS was prepared in horses by injection of human peripheral lymphocytes and rosette-inhibiting, cytotoxic and agglutinating titres were determined during immunization. The ALS had been tested in vivo by regional administration to vervet monkeys bearing skin allografts. It was found t h a t the peak of rosette-inhibiting titre appeared to provide a good index of immunosuppressive activity. These peaks, and the accompanying periods of immunosuppressive activity, were of short duration, in contrast to the levels of cytotoxic and agglutinathig titres. Antihuman lymphocyte sera had considerable rosette-inhibiting titres against the lymphocytes of the baboon (Papio papio) but little against those of the vervet monkey (Cercopithecus aethiops). Inhibition by ALS of the phenomenon described by us is unaffected by complement. Antihuman globulin serum and phytohaemagglutinin had no inhibitory effect. Digestion of ALS with pepsin to obtain the F (ab')2 fragment had only a slight effect on rosette-inhibiting titres, while it reduced the cytotoxic activity very considerably. The phenomenon described by us is probably different from that reported by other workers, in which only a small proportion of lymphocytes form rosettes. [ABSTRACT FROM AUTHOR]

This paper describes technical details of a micro-reaction for the in vitro detection of agglutinating potency of antilymphocytic serum produced in rabbits with chicken, rat and dog thymus cells, The titration of antilymphocytic serum includes the use of microtitre plastic plates and lymphocytes treated with formalin and stained with trypan blue stain. Formalinized and stained lymphocytes represent a stable antigen of long durability, and the application of those cells in leucoagglutination increases the accuracy and sensitivity of the reaction. [ABSTRACT FROM AUTHOR]