Yukihiro Ibayashi

The regulatory effect of adherent cells on lymphokine activated killer cells

We analyzed the effect of adherent cells on the induction of lymphokine-activated killer (LAK) cell activity by depleting adherent cells from peripheral blood lymphocytes (PBL) or by adding adherent cells to PBL before culture with interleukin-2. We found that adherent cells clearly down-regulate LAK cell induction. These inhibitory effects are dependent on the number of adherent cells added. Inhibitory effects of adherent cells are abolished by the addition of indomethacin to the LAK culture. Soluble factors derived from adherent cells, such as interferons and interleukin-1, have a slight enhancing effect on LAK induction. In contrast, adherent cells appear to inhibit LAK induction primarily by producing prostaglandin E2(PGE2). PGE2 in turn inhibits the induction of LAK effector cells by inhibiting the expression of the transferrin receptor on LAK cells. These effects are manifested most strikingly in the early phases of LAK induction.

Modification of natural killer activity of lymphocytes infiltrating human lung cancers

SummaryThe purpose of these studies was to compare local and systemic human lymphokine activated killer (LAK) and natural killer (NK) cytotoxic activity and to determine its modulation by biologic agents. Local immunity may be an important component in limiting local tumor growth. Therefore, as a model for studying immune function in the local compartment, we assessed NK activity of lymphocytes present at the site of human tumors and in peripheral blood (PBL). We extracted tumor infiltrating lymphocytes (TIL) and PBL from patients with pulmonary tumors and compared NK activity and response to the biological modifiers gamma interferon (IFN-γ), indomethacin (INDO), and interleukin 2 (IL-2). We also studied TIL and PBL LAK activity using the NK-resistant M14 target cells and determined the TIL response to IL-2, plus IFN-γ. Titration of K562 targets in a 51Cr release assay revealed that untreated TIL have low cytotoxicity (4.32%) compared to untreated PBL (34.3%, P=<0.001). This low level of TIL NK activity was not affected by IFN-γ, INDO, or IL-2 at 1 h. However, at 3 days of culture, IL-2 with or without exogenous IFN-γ significantly increased TIL NK ctotoxicity (20.5%, P=0.02 without IFN-γ and 32.52 lytic units (LU), P=<0.02 with IFN-γ). Untreated TIL and PBL both had low cytotoxicity against M14 targets (1.08 LU and 1.26 LU), respectively. After 3 days culture with IL-2 plus IFN-γ, both TIL and PBL LAK cytotoxicity were increased (14.34 LU and 40.63 LU). We conclude that local NK and LAK activity is intrinsically low. However, this activity can be modulated by biologic agents, thus giving hope for the development of local antitumor effectors capable of in vivo tumor control.

The Heterogeneity of Target Recognition by Lymphokine‐activated Killer Precursor Cells

Lymphokine‐activated killer (LAK) cells were generated from peripheral blood lymphocytes (PBL) that were depleted of mature cytotoxic natural killer (NK) cells. PBL NK activity was abolished by pretreatment of effector cells with the toxic lysosomotropic agent l‐leucine methyl ester (LME) or by depletion of effector cells by K562 monolayer absorption (MA). Both treatments markedly reduced the proportion of cells expressing NK‐associated markers such as CD 16 (Leu 11b, B73.1), Leu 7, and NKH‐1 (Leu 19), whereas these treatments had minimal effects on cells expressing T cell markers (CD 3, CD 4, and CD 8). LME and MA also drastically decreased the proportion of K562 target‐binding lymphocytes. LAK activity against NK‐sensitive and NK‐resistant targets can be generated from the NK cell‐depleted PBL by incubation with interleukin‐2. Peak LAK activity generated from MA‐treated PBL was later than the peak of LAK activity generated from either untreated or LME‐treated PBL. Although MA of PBL on NK‐resistant S4 sarcoma targets had little effect on NK activity, LAK activity against both K562 and S4 targets was reduced. These results suggest that there are at least three LAK precursor subpopulations in PBL: mature NK cells that can bind and kill K562 targets (LME‐sensitive and MA‐sensitive); “pre‐NK”cells that can bind but cannot kill (LME‐resistant and MA‐sensitive); and non‐NK cells that cannot bind and cannot kill K562 targets (MA‐resistant).

Cancer and inflammation.

Inflammation is the succession of changes of a living tissue to injury and to the cause of injury, which can be regarded as hosts defensive reaction and repairing process of the injured tissue. On the other hand, cancer represents a pathologic disturbance of growth characterized by an excessive and unceasing proliferation of cells. It is assumed that when progressive growth of tumor injures the normal tissue active hosts defensive reaction against the tumor itself and subsequent injury may be expressed locally as inflammatory response.Our previous experiments with the autochthonous tumor system of the rat showed clearly that the intensity of the lymphocyte infiltration in the tumor tissue correlates with the tumor specific immune resistance. On the basis of the results, lymphocyte subpopulations and subsets infiltrating in various human cancer tissues were identified with antihuman lymphocyte monoclonal antibodies. It was demonstrated that the grade of lymphocyte infiltration, especially of T cells, in cancer tissue correlates with clinical prognosis. Furthermore, we performed functional analysis of tumor infiltrating cells in rat syngeneic tumor-host system. Various tumor infiltrating cells were shown to play an important role in eradicating the transplanted tumor. Killer/suppressor T cells were demonstrated to be the final effector cells recognizing specifically the target tumor cells. Thus the inflammatory response at the site of tumor can be regarded as the manifestation of host resistance against the tumor.