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This paper describes a T-cell targeting strategy based on the use of an antigen-monoclonal antibody heteroconjugate. A rat anti-idiotypic monoclonal antibody specific for a murine B-cell lymphoma was conjugated to the purified protein derivative (PPD) of tuberculin. This construct selectively delivered up to 4.5 &times 104 molecules of PPD onto each tumour cell. Targeted PPD was internalized for endosomal processing and was presented in association with the I-A class II restriction element to PPD-reactive T-helper (Th) cells. Activated Th cells were demonstrated to proliferate and secrete significant levels of tumour necrosis factor (TNF). Such lymphokine secretion was observed at a PPD concentration as low as 1 ng/mI. Despite the secretion of TNF, the S-cell lymphoma was found to be resistant to autonomous Th-mediated cytotoxicity. Targeted Th cells did, however, activate tumourcidal macrophages that subsequently mediated significant tumour cytostasis. Based on this observation, it is proposed that the targeting system described may be exploited as the basis for a future immunotherapeutic strategy. [ABSTRACT FROM AUTHOR]

T-colony formation can be induced in PHA-stimulated peripheral blood mononuclear cells (PBM) from man, but not in PHA-stimulated purified T cells, the latter requiring the presence of factors produced by PHA-stimulated PBM and termed T-colony promoting activity (TCPA). In this paper, we demonstrate that interleukin-2 (IL-2), the growth hormone of T lymphocytes, controls T-colony formation. We show that: (i) IL-2 activity and TCPA produced by PHA-activated PBM are co-purified by gel filtration and chromatography on blue agarose, a procedure which yields a 850-fold IL-2 purification; (ii) recombinant IL-2, produced by genetically manipulated Eseherichia coli, can induce T-colony formation in PHA-stimulated purified T cells; (iii) Monoclonal antibody against the IL-2 receptor (anti-Tac antibody) completely inhibits the T-colony formation in PHA-stimulated PBM when directly added to the culture system. [ABSTRACT FROM AUTHOR]

In this paper we present experiments that indicate that, in man, most T-celI subpopulations produce interleukin-2 (IL-2), but that the main cell subpopulation which produces it, both upon activation with phytohaemagglutinin or in autologous mixed lymphocyte cultures, is that of autologous rosette-forming (Tar) T4+ T cells. Conversely, the main IL-2-responding T-cell subpopulation is that composed of T cells depleted of Tar (T-Tar) that are T8+ IL-2 was also found to be more effectively produced by Tar cells that do not bind peanut agglutinin (PNA) than by those that do. The PNA T4+ Tar cells were also found to respond best to interleukin- I (IL-I). [ABSTRACT FROM AUTHOR]

IL-2 receptor expression by B cells has previously been considered to be confined to activated normal B cells and, among the B cell leukaemias, to the hairy cells (HC) of hairy-cell leukaemia. In the present paper, using α-Tac monoclonal antibodies in a highly sensitive indirect rosette method, we show that both normal and certain leukaemic B cells other than HC express IL-2 receptors. The density of these receptors is low since they were not detectable by indirect immunofluorescence. Various controls excluded non-specific-reagent or exogenous receptor binding and blocking studies with recombinant IL-2 confirmed the presence of the IL-2 receptors. The significance of the findings is discussed and it is suggested that B cell IL-2 receptor expression without in-vitro activation may be a function of B cell maturity. [ABSTRACT FROM AUTHOR]