[Influence of erythropoietin on immunological system of patients with chronic renal failure].

UNLABELLED

Recombinant human erythropoietin (epoetin) administration is a well established therapy of anaemia in maintenance hemodialysis (HD) patients. During the treatment, along with an increase in haemoglobin (Hb) level also an improvement of physical and sexual activity and cognitive functions was observed. Moreover, recent studies have shown an impact of epoetin on lipid-carbohydrate and protein metabolism, endocrinological functions and immune system [1-7]. It is still unclear whether all these changes are caused by direct epoetin activity or they are associated with the correction of anaemia and better oxygen supply and therefore an improvement of the conditions required for many metabolic function. The goal of the first study performed in our centre was to estimate the influence of epoetin alpha (Eprex) administered in the doses not affecting erythropoiesis (7-10 IU/kg/three times a week for 12 weeks) on serum levels of interleukin (IL) 2, 6 and tumor necrosis factor TNF-alpha [8, 9]. 10 HD patients (3 F, 7 M) aged from 33 to 62 years participated in that study. The level of IL-2, IL-6 and TNF-alpha was measured by means of bioassay using a highly sensitive cell line respectively CTLL, B9 and fibrosarcoma--WEHI 164 (clone 13). Cells viability was tested by colorimetric MTT assay. During the first period of observation stable Hb concentration and unchanged although significantly higher than in healthy people levels of TNF-alpha and IL-6 were noticed. Serum level of IL-2 increased significantly and in the 10 week it reached the values observed in healthy humans although after that period of time it dropped to the initial values. The aim of the following study was to estimate the influence of epoetin on IL-2, IL-10 and TNF-alpha production by whole blood cell culture [1, 2]. 10 HD patients (2 F, 8 M) aged from 35 to 53 years receiving standard doses of epoetin alpha (Eprex) for six months (in vivo experiments) and another 10 HD patients (3 F, 7 M) aged from 40 to 60 years not receiving epoetin participated in the study (in vitro experiments--cell culture were stimulated with different doses of (epoetin alpha--Eprex and epoetin beta--Recormon): 0.05; 0.1; 0.5; 1.0 IU/ml). IL 2 and TNF-alpha were measured using the bioassay mentioned above, IL 10 by ELISA immunoassay. The levels of IL10 increased in all epoetin treated patients and it was accompanied by transitory decrease of TNF-alpha. The levels of IL-2 increased in 7/10 patients under the study. Addition of epoetin in vitro to the whole blood culture of HD patients before implementation of epoetin confirmed that it is able to directly stimulate IL-2 production. The highest levels of stimulation of IL-2 secretion were observed for the physiological doses of epoetin (0.05 IU/ml). The aim of the more recent study was to examine changes in CD4+ and CD8+ T-cell subpopulations, the expression of the inhibitory molecule, CD152+ on T lymphocytes and the levels of IL-2, IL-6, IL-10, IL-12 and TNF-alpha in HD patients [10]. Additionally serum levels of C reactive protein (CRP), C3, C4 components of complement and immunoglobulin IgG, IgM and IgA were measured. 14 patients (8 F, 6 M) aged from 31 to 64 years receiving standard doses of epoetin alpha (Eprex) for twelve months (in vivo experiments) and another 4 HD patients (2 F, 2 M) aged from 43 to 57 years not receiving epoetin participated in the study (in vitro experiments--cell culture were stimulated with epoetin as in previous study).

METHODS

IL-2, IL-6, and TNF-alpha were measured using bioassays described above, IL-12 and IL-10 by ELISA immunoassay. Expression of T-cell surface molecules was measured both in vivo by flow cytometry of lymphocytes sampled from peripheral blood and in vitro using whole blood cell culture stimulated with physiological as well as non-physiological doses of epoetin. The levels of C3, C4, IgG, IgM and IgA were estimated using nephelometric method. Compared with the findings before the start of epoetin therapy the CD4+/CD8+ ratio increased after 1 year of follow-up, whereas the percentage of CD152+ peripheral blood lymphocytes decreased. The increase of the CD4+/CD8+ ratio was dependent on a decrease of the percentage of CD8+ cells. The decrease of CD152+ population affected mainly CD8+152+ T cells. All these effects became apparent after 6 months of epoetin treatment. In vitro stimulation of whole blood cultures revealed that the addition of physiological concentration of epoetin decreased the percentage of CD8+152+ T cells. The pattern of the cytokines shifted towards Th1 phenotype (increase of IL-2 and IL-12) with a decreased level of proinflammatory cytokines (decrease of IL-6 and TNF-alpha). Treatment with epoetin did not alter plasma CRP, C3, C4 components of complement, immunoglobulin, as well as total count of lymphocytes. Summing up, administration of epoetin to maintenance HD patients not only treats the anaemia but also results in favourable changes in immune system. Epoetin is probably not only hemopoietic factor but also an immunomodulatory cytokine.