High-performance liquid chromatographic separation of distinct epidermal cell-derived cytokines

Cytokine assays: an assessment of the preparation and treatment of blood and tissue samples

Cytokines are key components of the innate and adaptive immune system. As pivotal players in the progression or regression of a pathological process, these molecules provide a window through which diseases can be monitored and can thus act as biomarkers. In order to measure cytokine levels, a plethora of protocols can be applied. These methods include bioassays, protein microarrays, high-performance liquid chromatography (HPLC), sandwich enzyme-linked immunosorbent assay (ELISA), Meso Scale Discovery (MSD) electrochemiluminescence and bead based multiplex immunoassays (MIA). Due to the interaction and activity of cytokines, multiplex immunoassays are at the forefront of cytokine analysis by allowing multiple cytokines to be measured in parallel. However, even with optimized protocols, sample standardization needs to occur before these proteins can optimally act as biomarkers. This review describes various factors influencing the levels of cytokines measured in plasma, serum, dried blood spots and tissue biopsies, focusing on sample collection and handling, long term storage and the repetitive use of samples. By analyzing how each of these factors influences protein levels, it is concluded that samples should be stored at low temperatures in order to maintain cytokine stability. In addition, within a study, sample manipulations should be kept the same, with measurement protocols being chosen for their compatibility with the research in question. By having a clear understanding of what factors influence cytokine levels and how to overcome these technical issues, minimally confounded data can be obtained and cytokines can achieve optimal biomarker activity.

Keratinocyte-derived interleukin 3

Interleukin 3 (IL 3) initially was described as a cytokine which is produced by murine T lymphocytes and has multicolony stimulating factor (CSF) activity, activates mast cells and induces the proliferation of hematopoietic stem cell lines. In addition to T cells murine keratinocytes also produce an IL 3-like factor which according to its biological, biochemical and antigenic properties is indistinguishable from murine T cell IL 3. Moreover, by Northern blot analysis murine keratinocytes were found to express mRNA homologous to T cell IL 3 cDNA. Similarly, human keratinocytes have been shown to release an IL 3-like cytokine which also enhances the activity of natural killer cells and stimulates the release of oxygen radicals by granulocytes. However, human IL 3 mRNA could not yet be detected in human epidermal cells or epidermoid carcinoma cell lines. These findings indicate that human keratinocyte IL 3 appears to be distinct from T cell IL 3. Nevertheless, the exact nature of this cytokine remains to be clarified by sequence analysis and gene cloning. Through the production of these cytokines with IL 3-like capacity keratinocytes may participate in the regulation of the activity of different hematopoietic cells and thereby turn on early nonspecific host defense mechanisms against transformed cells and various harmful microbial organisms.

Human keratinocytes and epidermoid carcinoma cell lines produce a cytokine with interleukin 3-like activity

Keratinocytes are capable of releasing distinct immunomodulating cytokines such as epidermal cell-derived thymocyte activating factor (ETAF) and an epidermal cell-derived natural killer cell augmenting factor (ENKAF). The present study was performed to determine whether human keratinocytes also may secrete an interleukin 3 (IL-3)-like mediator and thereby participate in the regulation of mast cell activity in the skin. Supernatants of freshly isolated human epidermal cells (EC) and malignant keratinocyte cell lines (A 431, SCC) were tested for their capacity to induce the proliferation of IL-3-dependent cell lines 32 DCL and FDCP. Human epidermal cell interleukin 3 (EC IL-3) is spontaneously released by freshly isolated EC, A 431, and squamous cell carcinoma (SCC) cells. However, both normal EC and A 431 cells produced increased levels of EC IL-3 activity when cultured in the presence of different stimulants, such as phorbol myristate acetate and lipopolysaccharide. The EC IL-3 activity was not inhibited when treated with a monoclonal anti-IL-1 or anti-IL-2-antibody. Biochemical characterization showed that human EC IL-3 has a molecular weight of 17K, elutes of DEAE-ion exchange high-performance liquid chromatography (HPLC) as one major peak at 0.36 M NaCl, and upon HPLC-chromatofocusing exhibits 3 isoelectric points of 7.8, 7.5, and 5.6. Upon reversed-phase HPLC, EC IL-3 activity eluted at about 100% acetonitrile. When highly purified EC IL-3 was labeled with 125I and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, a single homogeneous band exhibiting a molecular weight of 17K was seen, which correlated with the IL-3 activity and was free of ETAF/IL-1, IL-2, and interferon activity. These data indicate that human EC synthesize an IL-3-like cytokine which is distinct from ETAF/IL-1, IL-2, and interferon and thereby may participate in the regulation of mast cell activity during inflammatory and fibrotic, as well as hypersensitivity reactions.