Secondary cytokine production by lymphoid cells used in cellular immunotherapy

An acidic microenvironment impairs the generation of non-major histocompatibility complex-restricted killer cells

The microenvironment within solid tumours has often been shown to exhibit an acidic local pH. In recent studies we could demonstrate that an acidic extracellular pH (pHe) inhibits the non-major histocompatibility complex (MHC) -restricted cytotoxicity of immunocompetent effector cells. However, within tumours the activation of cytotoxic cells may already be impaired by low pHe. Therefore, we investigated the influence of acidic conditions on the generation of active killer cells. The cytotoxic activity of natural killer (NK) as well as lymphokine-activated killer (LAK) cells against K562, Daudi and Raji cells was analysed after an activation period of 3 days at pHe 7.2-6.5. A minor reduction of pHe from 7.2 to 7.0 during the culture period resulted in a strong inhibition of the natural cytotoxicity of NK cells. Furthermore, acidic pHe below 7.2 prevented the generation of activated LAK cells by interleukin-2 (IL-2). The cytotoxic capacity could not be reconstituted if cells cultured at a pHe of 6.5 were returned to physiological pH for another 24 hr. Analysis of the cellular subtypes within the various cultures did not reveal differences regarding the frequencies of NK cells, CD8+ T cells, or CD4+ T cells. However, an acidic pHe clearly inhibited the activation-induced increase of relevant adhesion molecules. The production of cytokines which are involved in the regulation of the cytotoxic process (tumour necrosis factor-alpha, interferon-gamma, IL-10, IL-12 and transforming growth factor-beta1) was also affected by pHe, as their release was strongly inhibited at pHe 7.0. Furthermore, we observed a considerable decrease in the metabolic activity of effector cells at acidic pHe. In summary, our findings suggest that an acidic microenvironment impairs the induction of an anti-tumoral immune response within solid tumours.

Experimental autoimmune prostatitis: in vivo induction of the autoimmune response to lymphocytic soluble factors. Alterations at the endocrine metabolism level

PROBLEM

In rats, immunization with male accessory gland (MAG) extract promotes experimental autoimmune vesicle prostatitis. A specific mononuclear cell-mediated immune response and prostate androgen metabolism impairment in MAG-immunized rats were observed. The possibility that lymphocytic soluble factors (SoFs) can regulate the local steroid metabolism in these rats directly was studied. We investigated whether the SoFs released by MAG-sensitized lymphocytes are capable of modifying the prostatic androgen metabolism and whether they induce histologic lesions "in vivo" when they are inoculated, carried by liposomes, into untreated rats.

METHOD OF STUDY

"In vitro" enzymatic [3H]-5 alpha-dihydrotestosterone bioconversion and histologic studies were performed with prostates from SoF-treated rats (LK rats). The obtained 3 alpha/beta-hydroxysteroid-oxidoreductase activities showed that LK rat values were significantly lower than in controls: 79.0 +/- 2.5 vs 158.7 +/- 10.2 pmol/min/mg protein, respectively (P < 0.01).

RESULTS

In the histologic studies, LK rat prostates showed focalized mononuclear infiltrates of various degrees, whereas control rats showed non-atypic modification of the gland.

CONCLUSION

These results indicate that SoFs (probably total lymphokines) contribute significantly to the pathogenesis of experimental autoimmune prostatitis, involving a biochemical relationship between immune reaction and the androgenic enzymatic inhibition in the prostate.

Interleukin-2 and human immunodeficiency virus infection: pathogenic mechanisms and potential for immunologic enhancement

A hallmark of human immunodeficiency virus (HIV) infection is the progressive loss of CD4+ T lymphocytes; however, qualitative defects in immune responses occur prior to the precipitous drop CD4+ T cell numbers. One of the first immunologic defects to be described in HIV-infected individuals is a deficiency in interleukin (IL)-2 production. The addition of IL-2 in vitro to cultures of mononuclear cells from HIV-infected individuals partially or completely restored certain defective cellular immune responses. However, production of or addition of IL-2 has also been associated with increased viral replication in infected T cells. These observations underscore the pernicious correlation between immune activation and HIV replication. However, recent in vitro and in vivo studies have provided promising preliminary results suggesting that, at least at certain stages of disease, the benefits of IL-2 mediated immune enhancement may outweigh or override the inductive effects of this cytokine on HIV production.

Induction of lymphokine-activated killing with reduced secretion of interleukin-1 beta, tumor necrosis factor-alpha, and interferon-gamma by interleukin-2 analogs

BACKGROUND

Interleukin-2 (IL-2)-based immunotherapy has been shown to effect clinical responses in 15-35% of patients with metastatic renal cell carcinoma or melanoma. Despite its clinical efficacy, many clinicians refrain from using IL-2 because of the associated toxicity. This toxicity is believed to be mediated by such secondary cytokines as IL-1, tumor necrosis factor (TNF), and interferon (IFN)-gamma, which are produced by the patient's IL-2-stimulated peripheral blood mononuclear cells (PBMCs).

METHODS

Human PBMCs were stimulated with 1 nM wild-type recombinant IL-2 (rIL-2) or IL-2 analogs (R38A or F42K) that preferentially bind to the intermediate affinity IL-2 receptor (IL-2R). PBMCs were activated for lymphokine-activated killer (LAK) activity in 4-h 51Cr-release assays, using Daudi target cells. Cytokine content in the culture supernatants was determined by enzyme-linked immunosorbent assay.

RESULTS

Both R38A and F42K were capable of generating substantial LAK activity. Maximal specific lysis was 54% for PBMCs activated by R38A and 52% for F42K-stimulated cells, in contrast to 64% for rIL-2. In addition, analog-stimulated PBMCs secreted 59% of the IL-1 beta, 25% of the TNF-alpha, and only 8% of the IFN-gamma produced in response to rIL-2 (all p < 0.01 compared with rIL-2-stimulated secretion; one-way ANOVA).

CONCLUSIONS

IL-2 analogs that preferentially bind the intermediate-affinity IL-2R retain the capacity to induce substantial LAK activity despite a greatly reduced secondary cytokine production. Therefore, such IL-2 analogs may provide an effective, yet less toxic means of cancer immunotherapy.

Survival characteristics of metastatic renal cell carcinoma patients treated with lymphokine-activated killer cells plus interleukin-2

The immunologic manipulation of patients with metastatic renal cell carcinoma using lymphokine-activated killer (LAK) cells in conjunction with systemic interleukin-2 (IL-2) has been examined under conditions in which the life-threatening toxicities associated with IL-2 treatment have been virtually eliminated. We have examined tumor regression in vivo as well as the survival characteristics of 12 patients with metastatic renal cell carcinoma following immunotherapy. Five of 12 (42%) patients experienced tumor regression exceeding 50 percent following treatment. To determine if immunotherapy had influenced the length of survival, all patients were followed until the time of death. Previous studies have characterized the length of survival of metastatic renal cell cancer patients according to a combination of risk factors unique for each patient. In this model, patients were categorized into risk groups based on the number of risk factors. Survival was found to be dependent on risk factors such as performance status, time from initial diagnosis, number of metastatic sites, recent weight loss, and prior cytotoxic chemotherapy. On completion of the LAK cell immunotherapy protocol, patients were categorized as nonresponders or responders. In addition, they were assigned to risk groups based on their unique profile of risk factors at the time of entry into the protocol. Using this model, we found the median survival of nonresponders (23 months) to be no different from responders (24 months), p > 0.05. This was directly attributable to differences in risk factors which characterized members in these two response groups. However, the observed median survival of nonresponders following therapy was 1.9-fold longer than their projected survival based on the risk factors. Furthermore, the observed median survival of responders was 3.4-fold longer than projected from their risk factors. These results suggest that regardless of response status to therapy, cellular immunotherapy may play a role in mediating a significant palliative effect on the metabolic characteristics of these patients leading to extended survival.