The generation of specific cytotoxic responses by human lymphocytes requires antigen and activities provided by a lymphokine supernatant

Chronic active hepatitis B. Interferon-activated natural killer-like cells against a hepatoma cell line transfected with the hepatitis B virus nucleic acid

In a rapid 51Cr release assay, peripheral blood mononuclear cells from 12 healthy donors did not lyse the hepatitis B virus deoxyribonucleic-acid-transfected human hepatoma cell line 2.2.15, but under the same experimental conditions they did lyse K562 cells. Peripheral blood mononuclear cells from 10 out of 16 patients with chronic active hepatitis B exhibited cytotoxic activity against 2.2.15 cells in the presence of a relatively reduced natural killer cell activity to the K562 cell target. Enhancement of the cytotoxic activity to 2.2.15 cells was statistically significant in the group of patients being treated with leukocyte alpha-interferon. The activity was not influenced by the degree of human leukocyte antigen type matching between effector and target, and was enhanced by depletion of T-cells and by in vitro interferon treatment. These results therefore support the concept of a natural killer-like cell activated by clinical administration of interferon in chronic active hepatitis B patients. This cell effector was lytic for the virus B negative HEP-G2 cells also. However, T-cells purified from a few patients failed to lyse the HEP-G2 while lysing the 2.2.15 target, thus indicating that a preferential recognition of the virus-infected target may be exerted by certain T-lymphocyte subsets. The use of the human leukocyte antigen type defined, highly differentiated, hepatitis B virus releasing 2.2.15 cell line as target for fresh lymphocytes in this cytolytic assay did not disclose cytolytic T-cells in an obvious way. Further manipulation of this system perhaps using T-cell clones may be the next step to exploit the investigative possibilities offered by the availability of the 2.2.15 cell target.

Resting (IL-2 non-responsive) precursors of human T cell receptor gamma delta-positive cells (TCR1 cells) are activated by a two signal process

Precursors of T cells expressing the gamma delta-T cell receptor (TCR1 cells) have been identified in a resting (IL-2 non-responsive) subpopulation of human peripheral blood mononuclear cells (PBMC). Activation of the TCR1 precursor cells into proliferating and cytotoxic cells requires two signals, viz. IL-2 and either activated T cells (autologous or allogeneic) or malignant melanoma cells (MM-170). The activation process is inhibited by 0.1 microgram/ml cyclosporine. CD3 expression on TCR1 precursor cells was low, since the precursor cells were not always adequately depleted by OKT3 plus complement. Natural killer cells were generated from the same resting subpopulation of PBMC and by the same set of activation stimuli as were the TCR1 cells, suggesting a common pathway for activation of both cell types.

Interferon treatment of chronic hepatitis B surface antigen (HBsAg) carriers. A description of the activation profiles of natural killer cells obtained with different schedules of administration in three subsets of carriers

By monitoring immunobiological parameters known to be influenced by interferon (IFN), the natural killer (NK) cell activity of 10 low replication (anti-HBe) virus B-DNA (HBV-DNA) hepatitis patients receiving rIFN alpha-A, of 5 anti-HBe/delta positive hepatitis patients treated with rIFN alpha-2, and of 6 high replication (HBeAg) HBV-DNA hepatitis patients on lymphoblastoid IFN was followed-up during therapy. Overall, strong and significant (p less than 0.01) shift to increase segregated with the low replication subset; the delta positive subset was non-significantly increased (0.30 greater than p greater than 0.2); the high replication subset was depressed in a nearly significant (0.10 greater than p greater than 0.05) manner. Kinetic studies showed the activation of the first subset to follow an early steep rise and a subsequent plateau as fitted with a quadratic curve (p = 0.02); an early rise and a depression at 2 months delineated a complex cubic model (p = 0.06) in the high replication subset. The profound NK depression was clinically witnessed by a sharp rise of the aminotransferases and following drop of viremia. The study shows that i. discrete patterns of NK response as amenable to mathematical models may associate to differential patterns of virus B replication in patients responding to IFN; ii. point(s) on the NK curve may acquire clinical meaning as they coincide with a consensual or opposite shift of a clinical index.

Cellular cytotoxicity assessed by the 51Cr release assay. Biological interpretation of mathematical parameters

This study deals with the interpretation of primary data of the 51Cr release assay for cellular cytotoxicity. In particular the dose-effect relationship between increasing numbers of lymphoid cells and the percentage of target cells killed has been considered. The number of target cells killed depends on the frequency and the activity of cytotoxic cells. These two parameters are often not distinguished from each other, which causes confusion and frequently results in vague descriptions of cytotoxicity data. Because in many cases not all cells in the target cell population can be lysed, we recommend the introduction of the plateau value for target cell kill. This maximum of target cell kill is a measure of the frequency of lysable target cells, but also depends on the cytotoxic cell activity. Description of the dose-effect curve by y = A(1 - e-kx) allows the simultaneous calculation of the maximum kill (A) and the frequency of cytotoxic cells (k) in the lymphoid cell population (x). Results are presented which indicate that A and k represent totally independent biological parameters the use of which permits a more objective description of cytotoxicity data.

Cyclosporin inhibits a two-signal mechanism for the generation of cytotoxic NK-like cells, from small lymphocyte precursors

Cytotoxic cells resembling NK cells are generated from CD 3- small, lymphokine (LK) nonresponsive precursor cells during an 8 day culture period with mitomycin C-treated autologous T cell blasts and LK. Recombinant interleukin 2 (rIL2) can replace LK in this coculture system. Both stimuli are required for the generation of the cytotoxic cells, which can then be maintained in short term cultures by LK alone. The generation of the cytotoxic cells was inhibited in cultures containing 0.1 micrograms/ml cyclosporin (Cys). Cys did not inhibit the LK dependent growth of the cytotoxic cells. Cys also inhibited the mitogen and LK dependent stimulation of purified T cells, but did not inhibit the LK dependent proliferation of T cell blasts. In contrast to the results for the generation of the cytotoxic cells, Cys did not inhibit the activation/growth of peripheral blood NK cells by LK or rIL2. These studies support the notion that the precursors of the NK-like cytotoxic cells are at an earlier stage of differentiation than peripheral blood NK cells responsive to LK alone, and that the precursor cells are triggered into a differentiation pathway leading to the NK-like cytotoxic cells by a two-signal mechanism.

Induction of cytotoxic activity in human lymphocytes against autologous and allogeneic melanoma cells in vitro by culture with interleukin 2

The influence of interleukin 2(IL2) on the cytotoxic activity of lymphocytes from patients with melanoma against autologous and a variety of allogeneic melanoma cells was studied. IL2 was produced from blood lymphocytes cultured for 24 h with phytohaemagglutinin (PHA) and purified by membrane chromatography to exclude PHA. Lymphocytes from 13 patients with melanoma at various clinical stages were cultured fro 6 days with IL2 (2 U/ml) and then tested for cytotoxic activity against autologous melanoma cells, three allogeneic melanoma and three non-melanoma cells. Autologous cytotoxicity was generated by culture with IL2 alone and was not increased by culture with both IL2 and autologous tumour cells. Marked increases in cytotoxic activity were also generated against the allogeneic target cells and were maximal against the NK-insensitive Chang target cells. Similar degrees of cytotoxicity were induced by IL2 stimulation of lymphocytes from melanoma patients, patients with nonmelanoma carcinoma and normal subjects against the allogeneic target cells. Cold target inhibition studies were carried out against IL2 induced autologous cytotoxicity in five patients. In four of five studies the autologous target cells inhibited more than the allogeneic target cells. There was no significant difference between the inhibition produced by allogeneic melanoma cells and that produced by non-melanoma cells. Similarly, in studies against allogeneic target cells, there was no significant difference in the inhibition produced by allogeneic melanoma compared to non-melanoma target cells. This applied irrespective of whether effector cells were from melanoma or non-melanoma subjects. These results suggest that lymphocytes from patients with melanoma are primed against autologous antigens in vivo and that provision of a second signal, IL2, in vitro can induce cytotoxicity against the autologous tumour. The cytotoxicity generated against the allogeneic target cells did not appear to have specificity to melanoma. Several results, such as the pattern of cytotoxicity against the target cells and change in cell surface markers on the lymphocytes during culture, suggested that cytotoxicity was mediated by activated T cells rather than by nature killer cells. These findings appear to have important implications both in the understanding of tumor host relationships and for the use of IL2 in therapy.

Lymphokine production by peripheral blood leucocytes: quantitation of T-cell growth factor activity for assessment of immune response capability

Mitogen stimulation of as few as 200,000 human peripheral blood leucocytes (PBL) in 0.2 ml volumes produces highly active lymphokine supernatants. The lymphokine activity measured is T-cell growth factor. Under optimum conditions of PHA-P concentration, serum source and concentration, and time, activity is detectable to a dilution of between 1/250 and 1/700 for lymphokine supernatants from PBL of normal donors. Lymphokine supernatants prepared from PBL of donors previously treated with the immunosuppressive regimes of radiotherapy and/or chemotherapy had activities that were between 13% and 66% of normal controls. Lymphokine production as a quantitative measure of immune capability is discussed.