Age-dependent decline of natural killer and antibody-dependent cell mediated cytotoxicity activity of human lymphocytes is connected with decrease of their acid phosphatase activity

Cigarette smoking is associated with the reduction of lymphokine-activated killer cell and natural killer cell activities

Lymphokine-activated killer (LAK) cell and natural killer (NK) cell activities were determined in a group of healthy individuals with differing smoking habits. The study population consisted of 54 Japanese males, including 23 smokers, 8 ex-smokers and 23 non-smokers. Peripheral blood mononuclear cells (PBMC) were isolated and used as effector cells. LAK cells were generated by incubation of PBMC with interleukin-2 for 72 h. LAK cell activity against NK-resistant Raji cells and NK cell activity against NK-sensitive K562 cells were examined by 4-h51Cr-release assay. LAK cell activity in the smokers was significantly lower than that in the nonsmokers. The smokers showed significantly lower NK cell activity than the nonsmokers, whereas NK cell activity of the ex-smokers was comparable to that of the non-smokers. The proportion of NK cells (CD3-16+56-, CD3-16-56+, or CD3-16+56+ cells) in the smokers was significantly lower than that in the nonsmokers. The present study demonstrates for the first time that cigarette smokers have lower LAK cell activity than nonsmokers.

Restoration of the immune functions in aged mice by supplementation with a new herbal composition, HemoHIM

The effect of a new herbal composition, HemoHIM, on immune functions was examined in aged mice, in which various immune responses had been impaired. The composition HemoHIM was prepared by adding the ethanol-insoluble fraction to the total water extract of a mixture of three edible herbs, Angelica Radix, Cnidium Rhizoma and Paeonia Radix. Supplementation to the aged mice with HemoHIM restored the proliferative response and cytokine production of splenocytes with a response to ConA. Also, HemoHIM recovered the NK cell activity which had been impaired in the aged mice. Meanwhile aging is known to reduce the Th1-like function, but not the Th2-like function, resulting in a Th1/Th2 imbalance. HemoHIM restored the Th1/Th2 balance in the aged mice through enhanced IFN-gamma and IgG2a production, and conversely a reduced IL-4 and IgG1 production. It was found that one factor for the Th1/Th2 imbalance in the aged mice was a lower production of IL-12p70. However, HemoHIM restored the IL-12p70 production in the aged mice. These results suggested that HemoHIM was effective for the restoration of impaired immune functions of the aged mice and therefore could be a good recommendation for immune restoration in elderly humans.

Natural killer (NK) cell function is a strong prognostic factor in colorectal carcinoma patients treated with the monoclonal antibody 17-1A

Tumor cells might be susceptible to different effector functions of the immune system. This cytotoxic capacity has been utilized to analyze the prognostic significance of peripheral blood mononuclear cells (PBMC) in patients with metastatic colorectal carcinoma (CRC) treated with the monoclonal antibody (MAb)17-1A. Such analysis might form the basis for future patient selection and may lead to improvements in therapeutic strategies. Between 1986 and 1998, 73 patients were treated with regimens containing MAb17-1A. Prior to therapy, the lytic capability of PBMC was assayed against: K562 (4 hr assay), the CRC cell line SW948 (4 hr and 18 hr assays) and antibody-dependent cellular cytotoxicity (ADCC, 18 hr assay). Since the study was performed over 13 years, the assays were checked for time-related bias. Reproducibility over time was satisfactory. Patients exhibited a significantly higher cytotoxic capability in all 4 assays compared to healthy control donors. No correlation to clinical outcome was noted for 18 hr ADCC and 18 hr spontaneous cytotoxicity. Pretreatment natural killer (NK) cell cytotoxicity (K562) was significantly related to overall survival (OS), progression-free survival (PFS), and response rate. OS for patients with high and low NK cell cytotoxicity was 71 vs. 30 weeks, respectively (p = 0.007). NK cell cytotoxicity (K562) was an independent prognostic factor for OS (p = 0.016). Pretreatment NK cell activity is a strong prognostic factor for patients with metastatic CRC receiving MAb17-1A therapy and is a predictor for OS, PFS and response. These results should be considered when designing antibody-based therapeutic protocols.

Enhancement of leukocyte functions in aged mice supplemented with the antioxidant thioproline

Previous research has shown that supplementation of the diet with thioproline (thiazolidine-4-carboxylic acid), an intracellular sulfhydryl antioxidant and free radical scavenger, increases mouse life span and stimulates the immune system. In the present study aged Swiss mice (20 month old) fed thioproline (0.07%,w/w) for 5 weeks were used. Twelve month and 20 month old mice fed standard diet were used as controls. The lymphoproliferative response to the mitogen Concanavalin A (Con A) and the mobility of lymphocytes, both spontaneous and directed to a chemoattractant gradient (chemotaxis), as well as antibody-dependent cellular cytotoxicity (ADCC) and natural killer (NK) activity of leukocytes, were measured in cells from spleen and thymus. All of the above functions showed a significant decrease in aged (20 months) in comparison to adult mice (12 months). In aged animals, the ingestion of thioproline stimulated significantly the functions studied. Moreover, the age-related stress, revealed by the high corticosterone levels, was significantly decreased in animals fed this antioxidant. These data suggest that thioproline enhances immune response in the aged.

Increased natural killer cell cytotoxicity in Alzheimer's disease may involve protein kinase C dysregulation

Increased cytokine-mediated cytotoxic natural killer (NK) cell activity has recently been demonstrated in patients with senile dementia of the Alzheimer's type (SDAT). In the present study, we evaluated whether protein-kinase C (PKC), a main regulatory enzyme involved in the mechanism of exocytosis by NK cells, has a role in the cytotoxic response of NK cells (during IL-2 and IFN-beta exposure) from SDAT patients. Our data demonstrate the presence of an increased cytotoxic response by NK cells to IL-2 (mean increase +102%) and IFN-beta (mean increase +132%) in SDAT patients in comparison with healthy elderly subjects (+75% and +88% for IL-2 and IFN-beta, respectively). A smaller suppression of NK cytotoxicity after cortisol was also observed in SDAT (mean decrease -24%) than in the control group (-44%). The NK cell activity of SDAT patients was inversely correlated with the cognitive status as evaluated by the analysis of MMSE (Mini Mental State Examination) score. A comparison of young and elderly healthy subjects revealed no variations in NK cell activity. A physiological decrease in cytosolic PKC activity was demonstrated in healthy old subjects after IL-2 and IFN-beta incubation, but not in SDAT patients, while no variations in kinase activity were observed after cortisol incubation. The decreased activity with cytokines was associated with reduced levels of PKC alpha and betaII isoforms. An alteration in cytokine-mediated NK cell activity associated with PKC dysregulation is therefore suggested to occur in patients with SDAT. These changes may indicate the existence of an immunological component to the pathogenesis and progression of the disease.

Senescence and cytokines modulate the NK cell expression

We have been investigating senescence-related changes in human peripheral blood natural killer (NK2) cells. Data accumulated so far consistently and clearly show that both basal and cytokine (IL-2 and interferon alpha and gamma) induced antitumor MHC-unrestricted cytotoxic activity of NK cells are well-preserved in the healthy elderly. To investigate if the non-cytotoxic functions of NK cells are also spared from the influence of senescence, recombinant IL-2-inducible secretion of IFN-gamma, which serves as a first line of defense, was examined. The amount of IFN-gamma secreted by purified, 18 h activated NK cells from the elderly was only 25 percent of that released by the cells from the young. Thus, the type 1 cytokine-inducible cytotoxic and cytokine secretory functions appear to be dissociable properties of NK cells, at least in the elderly. However, this aging-related early phase secretory deficit could be overcome by chronic stimulation with IL-2 (7 day culture). Since different subsets could perform different functions, we analyzed the NK subsets by flow cytometry. A minor CD56bright subset and a major CD56dim subset could be distinguished based on the density of expression of the cell surface CD56 molecule (N-CAM). We inquired if immunosenescence is likely to impact the steady-state level of circulating NK subsets. A significant decrease (P < 0.01) in percent CD56bright among CD56+ cells was observed in the elderly with a relative sparing of the CD56dim subset. The CD56bright/CD56dim ratio, perhaps representing NK cell maturity status, declined with age. This maturation-related subset redistribution and partial loss during aging of high affinity IL-2 alpha beta gamma receptor bearing 'immature' CD56bright NK cells has not been reported before. It could be a consequence of the decline in the level of IL-2 during aging. It is concluded that post-adolescent age-associated modulations in human NK cells are not expressed uniformly; they are pronounced in some, subtle in others but negligible in yet other biological parameters.

Elderly high NK responders are characterized by intensive proliferative response to PHA and Con A and optimal health status

In this paper we verify a hypothesis emerging from recent immunogerontological studies assuming that an elevated level of NK activity in the elderly may be regarded as a factor compensating for a decreased reactivity of T cells. According to this assumption a high NK activity should be associated with a poor reactivity of T cells. In our study the mitogenic responses of lymphocytes of the elderly and the young high and low NK responders to phytohemagglutinin (PHA) and Concanavalin A (Con A) were measured. A high level of NK activity was not found, as would be expected from the hypothesis, to be associated with a poor reactivity to PHA and Con A. In contrast, the mitogenic response to PHA and Con A was intensive in both the young and old high NK responders while weak proliferative responses to T cell mitogens were characteristic of the young and old low NK responders. Thus, our results do not support the assumption of an association between a high NK activity and a low proliferative response to T cell mitogens in the elderly. We also found that both the elderly and the young high NK responders were characterized by an optimal health status.

Coexistence of reduced function of natural killer cells and osteoclasts in two distinct osteopetrotic mutations in the rat

Recent evidence suggesting that immune cells and their products (cytokines) play an important role in the regulation of skeletal development and function, particularly of the osteoclast, implies that immune cell dysfunction may be involved in the pathogenesis of certain skeletal disorders. The mammalian osteopetroses are a pathogenetically heterogeneous group of skeletal disorders characterized by skeletal sclerosis resulting from reduced osteoclast-mediated bone resorption. Using a 51Cr-release microcytotoxicity assay we demonstrated that splenic natural killer (NK) cell activity was significantly reduced in two distinctly different osteopetrotic mutations in the rat, osteopetrosis (op) and toothless (tl). To determine whether this reduction in NK cell-mediated cytotoxicity is caused by decreased cell number and/or function in these osteopetrotic mutants, we quantitated NK cells by analyzing mononuclear cell suspensions labeled for two-color fluorescence with OX8 and OX19 monoclonal antibodies in a fluorescence-activated cell sorter. Flow cytometry of these double-labeled cells revealed that the percentage of NK cells (OX8+/OX19- subset) in op and tl spleens was not significantly different from that of normal spleens. These results suggest that NK cells in these osteopetrotic mutants are functionally defective. Thus aberrations in osteoclast and NK cell function coexist in these mutations, and their developmental relationships deserve further study.

Immune dysfunction in the elderly: effect of thymic hormone administration on several in vivo and in vitro immune function parameters

The effects of short-term thymic hormone administration on age-associated immune function were evaluated. Two groups of individuals greater than 65 years of age were treated for 30 days with thymic extracts (TP1) or placebo; before and after this treatment a panel of in vitro and in vivo parameters was determined according to a very rigorous experimental protocol. In most individuals, TP1 treatment was associated with an improvement in cutaneous delayed-type response to PPD. Moreover, an increase in a circulating T cell subpopulation bearing the CD45R surface antigen ("virgin" T cells), and in NK cell cytotoxic activity was also observed in some subjects. Finally, lymphocyte responsiveness to PHA tended to increase, while no effect on lymphocyte ability to produce IL-2 following mitogen stimulation was observed. These findings suggest that TP1 treatment may influence age-related alterations in immune function parameters in some subjects.

Biology of natural killer cells

Studies of cytotoxicity by human lymphocytes revealed not only that both allogeneic and syngeneic tumor cells were lysed in a non-MHC-restricted fashion, but also that lymphocytes from normal donors were often cytotoxic. Lymphocytes from any healthy donor, as well as peripheral blood and spleen lymphocytes from several experimental animals, in the absence of known or deliberate sensitization, were found to be spontaneously cytotoxic in vitro for some normal fresh cells, most cultured cell lines, immature hematopoietic cells, and tumor cells. This type of nonadaptive, non-MHC-restricted cellmediated cytotoxicity was defined as “natural” cytotoxicity, and the effector cells mediating natural cytotoxicity were functionally defined as natural killer (NK) cells. The existence of NK cells has prompted a reinterpretation of both the studies of specific cytotoxicity against spontaneous human tumors and the theory of immune surveillance, at least in its most restrictive interpretation. Unlike cytotoxic T cells, NK cells cannot be demonstrated to have clonally distributed specificity, restriction for MHC products at the target cell surface, or immunological memory. NK cells cannot yet be formally assigned to a single lineage based on the definitive identification of a stem cell, a distinct anatomical location of maturation, or unique genotypic rearrangements.

Exogenous growth hormone treatment alters body composition and increases natural killer cell activity in women with impaired endogenous growth hormone secretion

In order to assess the potential relationship between human growth hormone (GH) and body composition (BC) and natural immunity (NI), we measured the effects of exogenous GH on fat weight (FW), fat-free weight (FFW), and the cytotoxic activity of natural killer (NK) cells in women with impaired GH secretion. Mean peak serum concentrations of GH in response to L-dopa/arginine stimulation were 6.2 +/- 1.1 (SEM) ng/mL in 6 untreated subjects (US) and 5.4 +/- 1.5 ng/mL in 6 GH-treated subjects (TS). Moreover, the pretreatment circulating levels of IGF-I were low in both groups (US 684 +/- 121 mU/mL and TS 583 +/- 83 mU/mL), and they correlated with pretest levels of NK cell activity (r = .59, P less than .05) when both groups were combined. The TS were given 700 micrograms of human GH IM for an average of 14 days while the US were studied in parallel without GH treatment. As measured by hydrodensitometry or skinfold anthropometry, FW decreased (26.1 +/- 6.8 kg to 23.8 +/- 6.3 kg, P less than .05) and FFW increased (44.9 +/- 3.3 kg to 46.2 +/- 3.8 kg, P less than .05) in the TS. In the US, there were no significant (P less than .05) changes in either FW or FFW. Using a standard 51Cr release assay to measure the specific lytic (SL) activity of NK cells, mean SL activity increased from 24.4 +/- 7.0% to 44.1 +/- 8.9% (P less than .05) in the TS, whereas levels in the US were not altered significantly (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Activity of acid phosphatase in target binding cells expressing NK cytotoxic potential

Activity of acid phosphatase was analysed in the NK-effectors from human blood forming conjugates with K 562 cells. Presence of activity of acid phosphatase was associated with the cytolytic potential of the NK-effectors. The non-lytic target-binders did not express activity of this enzyme. The results suggest that activity of acid phosphatase in the effector cells of NK reaction is important in the lethal hit stage.

Expression of intracellular biochemical defects of lymphocytes in aging: proposal of a general aging mechanism which is not cell-specific

There is a decline in immune capacity with age which is expressed on the organismic level by association with numerous immune-related diseases, on the cellular level by impaired mitogenesis, on the biochemical level by impaired metabolic pathways, and on the molecular level by decreased protein synthesis and degradation. Defects in various cofactors such as calcium and several nucleotides also occur and may be related to the impaired enzyme function during mitogenesis in the aged. The central cause for decreased mitogenesis in the aged could be a decrease in protein synthesis which appears to cause impaired enzyme induction. This impaired enzyme induction accounts in part for the decreased glycolytic flux and DNA synthesis in these cells. Decreased protein synthesis also has been associated with a decreased synthesis of lymphokines which help these cells to proliferate. Numerous other intracellular age-related defects of lymphocytes also occur which may collectively play important interdependent roles in the impaired lymphocyte function of the aged. A potential general underlying mechanism of cellular senescence is proposed based on a genetic "slowing-cycle" effect of transcription, translation, and enzyme induction with immunosenescence presented as an example of an expression of these basic defects.