In vitro growth of murine T cells. III. Method for separation of T cell growth factor (TCGF) from concanavalin A and biological activity of the resulting TCGF

Immersion in the search for effective cancer immunotherapies

Real innovations in medicine and science are historic and singular; the stories behind each occurrence are precious. At Molecular Medicine we have established the Anthony Cerami Award in Translational Medicine to document and preserve these histories. The monographs recount the seminal events as told in the voice of the original investigators who provided the crucial early insight. These essays capture the essence of discovery, chronicling the birth of ideas that created new fields of research and launched trajectories that persisted and ultimately influenced how disease is prevented, diagnosed, and treated. In this volume, the Cerami Award Monograph is by Steven A. Rosenberg, Chief of Surgery at the National Cancer Institute in Bethesda, Maryland, USA. A pioneer in the development of immunotherapies and gene therapies for advanced cancers, this is the story of Dr. Rosenberg’s scientific journey.

IL-2: the first effective immunotherapy for human cancer

The ability of IL-2 to expand T cells with maintenance of functional activity has been translated into the first reproducible effective human cancer immunotherapies. The administration of IL-2 can lead to durable, complete, and apparently curative regressions in patients with metastatic melanoma and renal cancer. The growth of large numbers of tumor-infiltrating lymphocytes with in vitro anti-cancer activity in IL-2 has led to the development of cell transfer therapies that are highly effective in patients with melanoma. The genetic modification of T cells with genes encoding αβ TCRs or chimeric Ag receptors and the administration of these cells after expansion in IL-2 have extended effective cell transfer therapy to other cancer types.

Production of mitogen-free immune interferon and T-cell growth factor by human peripheral blood lymphocytes induced with biotin-labeled staphylococcal enterotoxin A

A method for the facile removal of mitogens or inducers of lymphokine production from cell culture medium of stimulated cells is described. The technique is based on the covalent attachment of biotin to mitogen or inducer and the removal of the biotinylated products from stimulated cell culture medium using immobilized avidin. Using this procedure, biotin-labeled staphylococcal enterotoxin A (SEA-B) was shown not to differ significantly from unmodified SEA in its capacity to stimulate mitogenesis and induce production of immune interferon (IFN) and T-cell growth factor (TCGF) in cultures of human mononuclear cells from peripheral blood. SEA-B was also shown not to differ from SEA in its binding to SEA antibodies. Results of mitogenicity studies and competitive radioimmune assay (RIA) measurements indicate that SEA-B is essentially completely removed from stimulated cell culture medium by absorption with avidin coupled to Sepharose 4B.

Successful immunotherapy of natural killer-resistant established pulmonary melanoma metastases by the intravenous adoptive transfer of syngeneic lymphocytes activated in vitro by interleukin 2

In previous in vitro studies, we have shown that murine splenocytes or cancer patient lymphocytes incubated in IL-2 become lytic for fresh syngeneic or autologous tumors. We have now performed the adoptive transfer of such lymphokine-activated killer (LAK) cells in a murine B16 metastasis model to test their in vivo efficacy. 1 X 10(8) LAK cells, infused intravenously into C57BL/6 mice with established B16 pulmonary metastases, led to a marked decreased in the number of lung nodules and improved survival. LAK cells administered 3 d after amputation of a tumor-bearing limb also decreased the incidence of spontaneous pulmonary metastases. LAK cells generated from tumor-bearer splenocytes had effects equivalent to those from normal animals, and this antimetastatic effect of the LAK cells did not require the prior administration of cyclophosphamide or other immunosuppressants. Fresh or unstimulated splenocytes had no effect. The antitumor effectors and precursors in vivo and in vitro were Thy-1+. The lymphokine required for the activation appeared to be interleukin 2 (IL-2), since incubation in partially purified supernatants from PMA pulsed EL-4 or Con A-pulsed splenocytes or purified Jurkat IL-2 led to the generation of LAK cells equally active in vivo. The use of IL-2-activated cells may provide a valuable method for the adoptive therapy of human neoplasms as well.

Transplantation tolerance: evidence for Lyt 1+,2-,Qa 1.2+ Suppressor-inducer T cells in allogeneic thymus-grafted nude mice

Nude mice, of BALB/c genotype, grafted with thymus stroma become immunocompetent (R. Hong, H. Schultz-Wisserman, E. Jarreth-Toth, S. D. Horowitz, and D.D. Manning, J. Exp. Med. 149, 398, 1979; B. P. Chen and G. A. Splitter, Cell. Immunol. 51, 127, 1980), but are tolerant to the thymus-donor genotype. Using such mice to investigate the mechanism(s) of transplantation tolerance, it was found that maintenance of tolerance required active interactions of three subsets of T cells specific for alloantigens of the thymus-donor genotype: (i) Lyt 1+,2- helper T cells, (ii) Lyt 1-,2+ suppressor T cells, and (iii) Lyt 1+,2-,Qa 1.2+ suppressor-inducer T cells. In mixed-lymphocyte culture, helper T cells could be activated by alloantigens of the thymus-donor genotype, but clonal expansion of these helper T cells was inhibited by suppressor T cells with the same specificity. Furthermore, exogenous interleukin-2 (IL-2) could modulate this suppressor activity, which suggested that one consequence of suppression was to limit IL-2 available to effector T cells. The response of cultures to exogenous IL-2 also indicated that thymus alloantigen-specific helper T cells had functional IL-2 receptors. Last, the presence of Lyt 1+,2-,Qa 1.2+ suppressor-inducer T cells were essential for active suppression, as suppressor T cells could not prevent helper T cells from proliferating to thymus-donor alloantigens when Lyt 1+,2-,Qa 1.2+ cells were removed. Altogether, the data presented in this study indicate a feedback-suppression pathway that led to clonal silencing of effector cells in transplantation tolerance.

Studies with a spontaneous murine tumour--II. Transformation of non-inhibitory lymph node cells (LNC) of tumour bearers into tumour inhibitor cells in vitro

Syngeneic BALB/c mice repeatedly pre-exposed to mitomycin-c-treated cells of a 'spontaneous' tumour SP/N-1 failed to develop resistance against the same tumour when tested by cell transfer assays. No difference could be observed between tumour-bearer, tumour-pretreated or normal donor LNC, or spleen cells by this assay system. When tumour-bearer LNC were cultured in vitro for 45 hr in the absence of tumour cells, these LNC generated a relatively strong ability to suppress tumour outgrowth in vivo following cell transfers. The tumour suppression appears to be due to tumour cell destruction since observation over four months or more in some experiments failed to reveal the presence of tumours at the site of inoculation. These findings clearly demonstrate that naturally arising tumours so often considered as devoid of, or weak in, tumour-associated transplantation antigens (TATA) may not necessarily be so. Despite the fact that the syngeneic host may be capable of recognizing TATA as foreign, the immune response initiated may not progress to completion in at least a proportion of these tumour-host systems. The defect appears to reside in the failure of differentiation of the pre-effector cells into the mature effector form. We interpret this as being due to a strong activation of certain inhibitors of essential lymphokine mediators such as interleukin 2, needed for differentiation and expansion of effector cell clones. It remains to be seen whether the mechanism of non-responsiveness or weakness of the response against many other members of this category of tumours--the 'spontaneous' or natural tumours--can be explained on the same basis as that of the SP/N-1 system studied here.

Studies with a spontaneous murine tumour--I. Indetectibility of host immune resistance with tumour-activated elaboration of T cell stimulatory lymphokines in vitro

A spontaneous tumour SP/N-1 which arose in a BALB/c female mouse and histologically consistent with breast origin was studied in vivo and in vitro to assess host responses to the tumour. Examination by means of the established methods of tumour cell challenge and cell transfer assays following 'immunization' of the isogeneic host against the tumour failed to provide clear evidence of host recognition and reactivity. Cell transfers conducted using critical numbers of tumour cells in which tumour to spleen cell ratios of up to 1:1000 were employed did not show any sign of antitumour activity within the pretreated host spleen cells. Nor was there any evidence of host resistance when presensitized mice were challenged with graded doses of tumour cells ranging from 10(4) cells, with no take of tumours, to 5 X 10(4) cells, with total acceptance of the tumour by the challenged mice. Despite failures to demonstrate clear immune recognition of tumour by the above criteria, normal spleen cells when incubated with the tumour cells in vitro elaborated factors with stimulatory and possibly suppressive properties. At least one of these factors was shown to stimulate T cells as evidenced by stimulation of DNA synthesis in thymocytes. This could be shown readily in the presence of a submitogenic concentration of Con A.

Preparation of T cell growth factor free from interferon and factors stimulating hemopoietic cells and mast cells

A simple two-step method involving ammonium sulfate precipitation followed by hydrophobic chromatography is described for the separation of T cell growth factor (TCGF) from a number of other factors contained in medium conditioned by concanavalin A-stimulated spleen cells. Thus, granulocyte-macrophage colony-stimulating factor, P cell-stimulating activity, pluripotential stem cell-supporting activity and interferon activity were not detected in TCGF partially purified by these steps. T cell-replacing factor co-purified with TCGF. Macrophage activity factor (MAF) co-purified with TCGF, but the ratio of MAF to TCGF activities was reduced more than 20-fold relative to that in crude conditioned medium. All of the factors were present in the 50-80% saturated ammonium sulfate fraction, however, levels of concanavalin A were reduced by 98% in this step. TCGF, separated in this way from these other regulatory factors will be useful in experiments analyzing the actions of TCGF on mixed populations of cells.

Decline, in aging mice, of the anti-2,4,6-trinitrophenyl (TNP) cytotoxic T cell response attributable to loss of Lyt-2-, interleukin 2-producing helper cell function

The in vitro generation of cytotoxic T lymphocytes (CTL) specific for 2,4,6-trinitrophenyl (TNP)-modified syngeneic spleen cells is found to be almost invariably depressed in apparently healthy 18-month-old mice of the long-lived (BALB/c x C57BL/6)F1 hybrid strain. Studies of CTL production from Lyt-2+ thymus cells have suggested that pre-killer cells may require, for maturation into effectors, the presence of a soluble helper factor, interleukin 2 (IL2), produced by Lyt-2- cells which are themselves devoid of pre-CTL activity. We have therefore developed a petri-dish adherence technique for separating spleen cells into Lyt-2+ and Lyt-2- populations in order to test for helper and pre-killer activity independently. Pre-CTL function is measured by stimulating Lyt-2+ cells in the presence of exogenous IL2. Helper cell activity is tested by adding Lyt-2- cells to "indicator" populations of Lyt-2+ pre-CTL. Estimation of IL2 levels in medium conditioned by unfractionated, TNP-self-stimulated splenocytes provides a second measurement of helper cell function. Mice 18 months of age, when compared to 4 month-old controls, are found to retain nearly all of their pre-CTL activity, but to have lost sufficient helper cell activity to account for the decline in unseparated spleen cell cultures. Older mice also produce lower IL2 levels.

A simplified method for the production of murine T-cell growth factor free of lectin

A simple and rapid method for the production of TCGF free of lectin (LF-TCGF) is described. Murine splenocytes are exposed to 10--20 micrograms/ml Con A for 2 h before washing the cells and incubating them in medium for an additional 20 h. This procedure leads to the same titers of TCGF activity obtained when Con A is presented throughout the incubation time. The resulting TCGF preparation is free of Con A as evidenced by its inability to activate fresh resting lymphoid cells and by measurements using [3H]Con A in tracer amounts. The LF-TCGF is capable of growing activated but not resting lymphocytes and can lead to greater than 50-fold increase in the generation of cytotoxic cells in in vitro sensitizations to alloantigens.