What is the role of cytokines in immunosupression and immunostimulation? and which type of cytokines responsible?
That's a pretty broad question and one which could probably be answered comprehensively in the context of infection and/or inflammation in a good immunology textbook.
I would recommend Immunobiology by Janeway et al.,http://www.amazon.com/IMMUNOBIOLOGY-PB-Janeways-Immunobiology-Janeway/dp/0815341237/ref=sr_1_1?ie=UTF8&s=books&qid=1243448270&sr=8-1
yes, cytokines are involved in immunomodulation. Cytokines like IL-2 involved in Th1 response. IL-2 mediates its effects by binding to IL-2 receptors, which are expressed by lymphocytes, the cells that are responsible for immunity.
here some useful links
Cytokines are key regulatory molecules in the modulation of immune responses. Cytokines are a unique family of growth factors. Secreted primarily from leukocytes, cytokines stimulate both the humoral and cellular immune responses, as well as the activation of phagocytic cells. Cytokines that are secreted from lymphocytes are termed lymphokines, whereas those secreted by monocytes or macrophages are termed monokines. A large family of cytokines are produced by various cells of the body. Many of the lymphokines are also known as interleukins (ILs), since they are not only secreted by leukocytes but also able to affect the cellular responses of leukocytes. Specifically, interleukins are growth factors targeted to cells of hematopoietic origin. The list of identified interleukins grows continuously with the total number of individual activities now at 22. Here is a useful linkhttp://www.uptodate.com/patients/content/topic.do?topicKey=~UfttE9k9pxrrAM.
This 2nd link answers your questions more perfectly providing a table with the role of cytokines.http://themedicalbiochemistrypage.org/growth-factors.html