Masri et al. 2003 studied the impact of cytokine gene polymorphisms on graft acceptance in a cohort of 163 transplant patients and their donors. Expression rates of gene polymorphisms in graft recipients-donors cohort were determined using sequence-specific polymerase (SSP) PCR primers corresponding to high, intermediate, or low producers of TNF-α, TGF-β, IL-10, IL-6, and interferon. The results were compared with a control group consisting of normal healthy Lebanese individuals. TGF-β production was observed to be high (81.6%) in patients with biopsy-proven graph rejection compared to patients with normal graph function. Patients with high TGF-β, low IL-10, and low interferon were found to have the highest CMV infection rates. Similar patterns were observed in patients with cyclosporine toxicity. Masri et al. concluded that their study indicated association of TGF-β with cyclosporine toxicity, chronic rejection, and immunosuppression.

Meenagh et al. (2002) used PCR-SSOP method to detect the frequencies of IL2 polymorphisms in different populations, in order to identify global allelic variation and to establish a databank for future studies. Along with the other populations, 80 healthy Omani blood and bone marrow donors were also used in the study. Genomic DNA from these subjects was PCR amplified and resolved. Certain oligonucleotide probes were used to identify the regions of SNPs, by subjecting the PCR products to hybridization with digoxigenin-labeled probes and chemiluminescent detection procedures. With respect to the C and G alleles of IL-6 G147C polymorphism among the Omani population, the G allele (87.5%) predominated the C allele (12.5%), which was similarly of low frequency among the Zulu, Singapore Chinese and Mexican populations. This was reflected on the high frequency of the high producer genotype (GG 76.2%), followed by GC (22.5%) and CC (1.3%) genotypes.

Snoussi et al. (2005) investigated the potential association of the polymorphism of interleukin 6 (IL6) with the susceptibility, clinicopathological characteristics, and prognosis of breast carcinoma. The study included 200 unrelated control subjects (191 females and nine males) and 305 unrelated patients with breast carcinoma (301 females and four males). At the time of analysis, 65 patients experienced recurrence and 18 patients among them died from breast carcinoma (27.7%). Genomic DNA was extracted from peripheral blood leukocytes by a salting procedure. By performing polymorphism analysis of the IL6 gene, a significant increase in the frequency of the IL6 (-597) GA heterozygous genotype was observed in the patients with breast carcinoma compared to the controls (0.324 versus 0.235). Also, the frequency of the IL6 (-174) GC heterozygous genotype was higher in patients than in controls (0.321 versus 0.230). The study showed that the frequencies of the IL6 (-597) A and IL6 (-174) C alleles were lower in the Tunisian population compared to other populations. Therefore, Snoussi et al. (2005) concluded that there was an association between the IL6 (-597) GA and IL6 (-174) GC genotypes and an increase risk of breast cancer in the Tunisian population, but not with the IL6 (-597) A or IL6 (-174) C alleles. That could be attributed to the low number of IL6 (-597) AA and IL6 (-174) CC patients in the Tunisian population. The breast carcinoma- specific disease- free survival (DFS) rate was significantly shorter in the group of patient with the IL6 (-597) GG and IL6 (-174) GG genotype. The estimated 3-year DFS rate in the groups of patients with (-597) GG or (-174) GG genotypes was 92% and 99%.