Introduction:
Human interferon-g (IFN-g ) is a cytokine expressed by subsets of T cells and NK cells, that have been stimulated by antigens or mitogens. In addition to measurement of cytokines in serum samples, detection can be performed inside the cells producing these cytokines using flow cytometry. This enables identification of the immuno-phenotype of cytokine-producing cells by (multicolor) immuno-staining techniques. Recently, a (possible) functional activity could be recognized between different subtypes of T cells based on their difference in cytokine expression profile. Characterization of these cells may become important for the determination of the status of the immune-system in patients.

Application:
In response to penetration of foreign antigens in humans, a balanced network between humoral and cellular immune-responses will be elicited. Regulation is provided by cell-cell contact and by a complex array of cytokines, (soluble) factors produced by these cells. Cytokines, like interleukins (IL), can behave stimulatory or inhibitory, or can even perform both activities, depending on the (pre-) activation stage of the target cell. Lymphocytes, like T helper/inducer cells (TH cells) and cytotoxic/suppressor T cells (TCYT cells) play an important role in antigen-specific immune-responses. TH 1 cells (producing a.o. IL-2 and IFN-g ) seem to be involved in cell-mediated immune-responses, while TH 2 cells (producing a.o. IL-4, IL-5, IL-6, IL-9 and IL-10) appear to have an important role in humoral immune-responses. TH 1 cells and TH 2 cells seem to be derived from progenitor TH 0 cells, which can produce e.g. IL-2, IFN-g , IL-4 and IL-5. Both T helper types may produce variable amounts of IL-3, TNF-a , TNF-ß, and other cytokines. In addition, TCYT cells appear to show a similar difference in expression of certain cytokines, which may allow to introduce a disctinction between TC 1 and TC 2 cells. Much interest is focussing on the detection of the functional activity of T helper cells using multicolor immunnophenotyping in combination with intracellular detection of different cytokines. Clinically, a number of important correlations have been put forward. As stated above, TH 1 cells appear to be involved in cell-mediated immune-responses like in bacterial infections, development of auto-immune diseases and transplant rejection. Whereas, TH 2 cells appear to be involved in immune protection in response to allergens, but may also lead to allergenic reactivity. Furthermore, development of progressive disease in patients with HIV infection, may be accompanied by a shift from a TH 1 cell response to a TH 2 cell response. These findings can be important for the therapeutic approach of HIV during disease.

Specifications:
Clone 45-15 produces IgG1 immunoglobulins directed against human IFN-g (see ref. 1,2,3,4).

Characteristics:
Interferon-g is a 20-25 kDa molecular weight glycoprotein, as detected by SDS-PAGE in reducing conditions. Human IFN-g is produced by subsets of T cells and NK cells, that have been stimulated by antigens or mitogens. Without stimulation, IFN-g is produced in very low amounts, but levels are increased rapidly upon activation. IFN-g has an antiviral activity and multiple immunoregulatory functions. Upregulation of MHC Class I antigens of monocytes/macrophages and specific adhesion molecules (e.g. ICAM-1 and VCAM-1) on endothelial cells, IgG production by activated B cells, chemotactic activities, and local induction of inflammation.

Product Availability:
Anti- IFN-g , clone 45-15 is available in the following product form:

IQP-163R	Anti- IFN-g PE conjugated	50 tests/vial (0,5 ml)
IQP-163P	Anti- IFN-g Purified	50 tests/vial (0,5 ml)

Literature references:

1. Andersson, U. et al. Simultaneous production of interleukin-2, interleukin-4 and interferon-g by activated human blood lymphocytes. Eur.J.Immunol., 20, 1591-1596, (1990).
2. Jung, T. et al. Detection of intracellular cytokines by flow cytometry. J.Immunol. Methods, 159, 197-207, (1993).
3. Jung, T. et al. Interleukin-4 and interleukin-5 are rarely co-expressed by human T cells. Eur.J.Immunol., 25, 2413-2416, (1995).
4. Jung, T. et al. Decreased frequency of interferon-g and interleukin-2 producing cells in patients with atopic diseases measured at the single cell level. J Allergy Clin Immunol., 96, 515-527, (1995).
5. C.Prussin and Metcalfe,CC. Detection of intracytoplasmic cytokine using flow cytometry and directly conjugated anti-cytokine antibodies. J. Immunol. Methods., 188 , 117-128, (1995)..
6. Mosmann, T.R., and Sad, S. The expanding universe of T-cell subsets: TH1, TH2 and more. Immunol. Today, 17, 138-146, (1996).
7. Manettie, R. et al. CD30 Expression by CD8+ T cells producing Type 2 helper cytokines. Evidence for large numbers of CD8+ CD30+ T cell clones in Human Immunodeficiency Virus infection. J.Exp.Med., 180, 2407-2411, (1994).