Miniaturization of the standard 51Cr release assay for long term follow-up of NK activity of individual mice

Family adversity and autonomic reactivity association with immune changes in HIV-affected school children

OBJECTIVE

To explore whether primary school entry is associated with changes in immune system parameters in HIV-affected children. HIV-affected children are vulnerable to psychosocial stressors, regardless of their own HIV serological status.

METHODS

Data from 38 HIV-positive and 29 HIV-negative children born to seropositive women were obtained. Measures included family adversity questionnaires, autonomic nervous system (ANS) reactivity, and enumerative and functional changes in peripheral blood immune parameters.

RESULTS

In comparison with children who were HIV-negative, children who were HIV-positive at baseline had fewer CD4(+) T lymphocytes (mean [M] = 916 versus 1206 cells/mm(3) × 10(3); F = 7.8, p = .007), more CD8(+) cells (M = 1046 versus 720 cells/mm(3) × 10(3); F = 7.98, p = .006), and diminished natural killer cell cytotoxicity (M = -0.29 versus 0.41; F = 8.87, p = .004). School entry was associated with changes in immune parameters, but HIV status was not associated with the magnitude of changes. Changes in immune parameters after school entry were associated with family stress and preschool entry ANS reactivity. Highly ANS reactive children had either the greatest increase in CD8(+) cells after school entry or the greatest decrease, depending on reported levels of family adversity (B = 215.35; t = 3.74, p < .001). Changes in functional immune assays were significantly associated with the interactions between HIV status and ANS reactivity.

CONCLUSIONS

These results suggest that autonomic reactivity is associated with increased immunological sensitivity to adverse or challenging social contexts among children affected by HIV.

A novel one-step, highly sensitive fluorometric assay to evaluate cell-mediated cytotoxicity

In this study, a fluorometric method using alamarBlue has been developed for detecting cell-mediated cytotoxicity in vitro. AlamarBlue is a non-toxic metabolic indicator of viable cells that becomes fluorescent upon mitochondrial reduction. Specific lysis of targets by effector cells is quantified by comparing the total number of viable cells in wells containing effector and targets together, with wells where target and effector cells were separately seeded. Cell-mediated cytotoxic activity by alloreactive T cells and natural killer cells has been detected using a novel application of the alamarBlue technique. The assay that we have developed to detect cell-mediated cytotoxicity is extremely sensitive and specific and requires a significant lower number of effector cells than the standard 51Cr assay. Since alamarBlue reagent is non-toxic to cells and the assay can be performed under sterile conditions, effector cells may be recovered at the end for further analysis or cell expansion, if desired. Direct comparison of cell-mediated cytotoxicity measured by the alamarBlue method with the standard 51Cr release assay revealed that the former method is as specific and more sensitive than the conventional assay. Moreover, very small inter and intra-assay variations have been observed for alamarBlue cytotoxicity assays. In conclusion, this study shows that the alamarBlue assay is an extremely sensitive, economical, simple and non-toxic procedure to evaluate cell-mediated cytotoxicity that yields accurate results using a limited number of effector cells. Furthermore, since this assay is a one-step procedure, and does not involve any risk for the personnel, it may be useful to analyze automatically cell-mediated cytotoxicity in a large number of samples.

Use of [35S]methionine-labelled rat lymphoblasts in micro-cytotoxic and limiting dilution assays

When only limited numbers of effector cells are available for in vitro T cytotoxic determinations, standard assays cannot be performed. 51Cr is still the most commonly used marker of target cells in cytotoxicity assays but since the incorporation of this marker is low, especially in non-tumor cells such as lymphoblasts, larger numbers of both target and effector cells are required. Here we report the use of [35S]methionine-labelled rat ConA blasts in cytotoxic, micro-cytotoxic and limiting dilution assays. Regardless of whether [35S]methionine or 51Cr targets were employed, cytotoxic activities were identical when large numbers of target cells (10(4)) were used. The high uptake of [35S]methionine by ConA blasts (9 cpm/cell) permitted the use of a small number of target cells without any loss of sensitivity. Therefore, the number of effectors and targets required was dramatically reduced, especially with high E : T ratios such as 100 : 1. The use of low number of [35S]methionine-labelled rat ConA blasts as targets was also suitable for the measurement of alloreactive T cell precursor frequencies. This technique illustrates the possibility of studying T cytotoxicity in animal species lacking tumor target cell lines under experimental conditions where the availability of effector cells is limited and the optimal use of such cells becomes critical.

Human recombinant IL-4 decreases the emergence of non-specific cytolytic cells and favours the appearance of memory cells (CD4+CD45RO+) in the IL-2-driven development of cytotoxic T lymphocytes against autologous ovarian tumour cells

As IL-4 and IL-6 have also been reported to promote the development of T lymphocytes such as IL-2, we investigated their role in the development of specific cytotoxic T lymphocytes (CTL) against autologous ovarian tumours in mixed lymphocyte tumour cultures (MLTC). Peripheral blood lymphocytes (PBL) from five ovarian carcinoma (OC) patients were incubated with autologous OC cells at a PBL:OC cell ratio of 20:1 in IL-2 alone (50 U/ml for the first week and 200 U/ml thereafter) or with IL-4 (100 U/ml) and/or IL-6 (5 U/ml). Neither IL-4 nor IL-6 improved lymphocyte proliferation consistently. In contrast, IL-4 reduced significantly the development of LAK activity as assayed against Daudi cell line, and decreased modestly the emergence of natural killer (NK) activity as assayed against K562. This property was not shared by IL-6. The prevention of the development of non-specific cytolytic activity (LAK and NK activities) was much stronger when the MLTC was started with IL-4 in the absence of IL-2 during the first week in culture. A concomitant drop in NKH-1 expression (CD56) was observed. By inhibiting the emergence of non-specific cytotoxicity, IL-4 provided better evidence of the specific cytolytic activity directed at ovarian cells. In parallel, a significant increase in the generation of memory cells (CD4+CD45RO+) was observed with IL-4. In conclusion, in this model, IL-4 added before IL-2 decreases significantly the emergence of non-specific cytotoxic cells, and promotes the generation of memory cells. These properties may be of interest in the design of strategies aimed at obtaining tumour-specific cells for investigational and immunotherapeutic purposes.

Standardization of a micro-cytotoxicity assay for human natural killer cell lytic activity

Cytotoxicity assays are widely used to evaluate the functional activity of NK and T cells against tumour target cells and the release of radioactive sodium chromate from labelled target cells is still the most commonly used marker of target lysis in culture supernatants. We describe here the standardization of a micro-cytotoxicity test in which the number of cytolytic effector and tumour target cells have been decreased by a factor of 10. The release obtained by 500 tumour target cells was compared with the release obtained by 5000 target cells in the standard cytotoxicity assay for target:effector cell ratios from 1:1 to 1:100. Both gamma and beta emissions of the 51Cr isotope were evaluated to determine the assay release. The results obtained by the micro-cytotoxicity assay (500 target cells) were comparable to those of the standard assay (5000 target cells) and 51Cr release evaluation using the gamma counter was the most sensitive method of determining lytic activity using 500 tumour target cells. beta counter evaluation using solid phase scintillation was found to be a reproducible alternative method, even if the lytic curves cannot be compared with those obtained using the traditional method.

Effects of interferon-gamma and tumour necrosis factor-alpha on the development of cytotoxic T lymphocytes in autologous mixed lymphocyte tumour cultures with human melanoma

We have studied the influence of tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) on the development of cytotoxic T lymphocytes (CTL) against melanoma in mixed lymphocyte tumour cultures (MLTC). In these MLTC, TNF-alpha at 10(4) U/ml increased the expansion of the CTL up to 10(4)-fold over recombinant IL-2 (rIL-2) alone. IFN-gamma at 10(4) U/ml and combinations of TNF-alpha plus IFN-gamma at 10(2)-10(3) U/ml promoted the proliferation more variably. MLTC generated with rIL-2 showed a predominance of CD8+ cells, while 2 weeks of culture in the presence of IFN-gamma at 10(4) U/ml, or with IFN-gamma and TNF alpha at 1 x 10(2)-10(3) U/ml, favoured the emergence of CD4+ cell populations. The cytotoxic activity of the lymphocytes generated in these MLTC showed a consistent decline of K562 cytotoxic activity following exposure to the combination of IFN-gamma and TNF-alpha. Despite the altered T cell subset distribution with different combinations of cytokines, no consistent alteration in the specific anti-tumour cytotoxicity against melanoma was detected. These results suggest that TNF-alpha and IFN-gamma influence the activation, phenotypic, and functional outcome of MLTC-generated CTL, and may account for the phenotypic variations observed in T cell populations generated in vitro.

Hierarchical immunosuppression of regional lymph nodes in patients with head and neck squamous cell carcinoma

Patients with head and neck squamous cell carcinomas (HNSCCs) manifest defects in cell-mediated immune function. Previous studies in this laboratory have demonstrated regional alterations in the immunocompetence of draining lymph nodes (LNs) in HNSCC patients. In this investigation, we studied functional activity of lymphocytes from lymph nodes in different locations in the radical neck dissections (RNDs) from patients undergoing operations for HNSCC. Lymphocytes from nodes close to the primary tumor ("near" lymph nodes or NLN) exhibited a significant decrease in interleukin-2 (IL-2)-activated cytotoxicity when compared to lymphocyts from distant nodes ("far" lymph nodes or FLN). In addition, co-culture experiments suggested the existence of a soluble regulatory factor, produced by lymph nodes, that inhibited the development of lymphokine-activated killer (LAK) cells in vitro. Further experiments with conditioned supernatants from the lymph node cells confirmed the presence of this soluble inhibitory factor. The inhibitory effect is significantly greater in NLNs than in FLNS. This hierarchical phenomenon suggests a regional network of immunosuppression in HNSCC patients. It is likely that tumor- and lymph node-induced suppression plays a role in limiting the efficacy of current immunotherapy protocols in human beings. A greater understanding of mechanisms of local inhibition of immune function will aid in improving adoptive immunotherapy for treatment of cancers in human beings.

First place--Resident Clinical Science Award 1990. Suppression of lymphokine-activated killer cell cytotoxicity by a soluble factor produced by squamous tumors of the head and neck

Incubation of human peripheral blood lymphocytes (PBL) in the presence of interleukin-2 results in the generation of lymphokine-activated killer (LAK) cells that are highly cytotoxic to a variety of autologous and allogenic tumor targets. We have identified a noncytotoxic, soluble factor, produced by human squamous cell cancers of the head and neck, that profoundly inhibits the generation of LAK cytotoxicity. Inhibition of the generation of cytotoxicity was demonstrated with coculture of PBL and freshly disaggregated tumor cells in a Transwell two-chamber system. Alternatively, inhibition occurred when LAK cells were generated in the presence of tumor-conditioned supernatants alone. These effects were not observed with conditioned supernatants from autologous or allogenic lymphocytes, human fibroblasts, or the erythroleukemia cell line K562. The presence of this inhibitory factor(s) was not required during the entire period of LAK generation. Suppression of cytotoxicity, measured after 4 days of LAK generation, could also be demonstrated when the conditioned tumor supernatant was present in only the last 24 hours of incubation. Suppression is mediated by a heat-labile factor with a molecular weight of greater than 75 kd. These results suggest that LAK cytotoxicity may be significantly impaired by soluble immunoregulatory factors present within the tumor milieu of squamous cell carcinomas of the head and neck. Further characterization of these factors may lead to the development of more rational and effective forms of immunotherapy.

Lymphokine-activated killer cell activity in patients with primary and metastatic malignant liver tumors

Lymphokine-activated killer cells were generated from peripheral blood mononuclear cells of 33 patients with liver tumors (benign, 6; primary malignant, 10; metastatic, 17) and 10 healthy individuals. Although peripheral blood mononuclear cell yield was significantly lower (p less than 0.01) in patients with hepatocellular carcinoma or with metastatic colorectal cancer, natural killer activity in the peripheral blood mononuclear cell fraction was comparable in all groups tested. Optimal lymphokine-activated killer activity was demonstrated after 9 to 12 days of culture in recombinant interleukin 2. Lymphokine-activated killer activity, interleukin 2-induced lymphocyte proliferation and total lytic activity generated per culture in all patient groups studied were similar to those of normal control cells cultured under the same conditions. These in vitro data demonstrate the feasibility of obtaining lymphokine-activated killer cells from the blood of patients with liver tumors and provide a rationale for the future use of lymphokine-activated killer cells in adoptive immunotherapy of patients with primary and metastatic hepatic neoplasms.

Comparison of NK activity in mouse spleen and peripheral blood lymphocytes

Natural killer (NK) cells originating in mouse peripheral blood were studied with regard to their lytic activity against YAC-1 target cells and to their expression of asialo-GM1 marker on their surface. In Balb/c, CBA/LAK and A/J mice, PBL were found to be approximately twice as effective as splenocytes. Splenic and peripheral NK cells were shown by flow cytometry to have similar lytic potential per cell; the difference in NK activity found in the spleen and in PBL was solely due to the differences in the size of the NK cell population found in the two sites. Strain distribution of NK activity in PBL followed the same pattern observed in splenocytes. The difference in NK activity between CBA and Balb/c mice was shown to be due to the fact that the lytic potential per NK cell was approximately twice as high in the former.

Lymphocyte proliferation and cytotoxic assays using flat-bed scintillation counting

Lymphocyte 51Cr release and [3H]thymidine uptake assays were evaluated with respect to measurement of sample radioactivity using the flat-bed scintillation counter. 51Cr lysates were spotted onto a glass fibre filter sheet while [3H]thymidine-labelled cells were filtered onto a similar sheet using a cell harvester. The 96 samples were rapidly processed for counting, without removal of individual sample areas. Either form of preparation showed good linearity of count rate with the quantity of material on the filter. Reproducibility was good; the coefficient of variation for 96 samples being within 5%. The low background and high efficiency of this counter results in increased assay sensitivity and allows considerable economies in materials to be made. A commercial version of the counter has six counting heads permitting a high rate of sample throughput.