Expression of CD80 and CD86 on T lymphocytes and monocytes of asthmatic children

INTRODUCTION The concept of costimulation has changed the way of understanding how T cells recognise and respond to antigens . The current model of T cell activation requires two signals: Signal 1: It is only an initiation event. It requires T cell receptor recognition and binding to antigen presented by antigen presenting cells. However this signal alone is necessary but not sufficient to induce T cell proliferation. Signal 2: It is a costimulatory signal. It results from binding of one of both molecules of B7 family (CD80 and CD86) on antigen presenting cells to one of two receptors on T lymphocytes (CD28 and cytotoxic T lymphocyte antigen CTLA4). If both signals are provided, it results in T cell clonal expansion and in the induction of effector functions such as lymphokine production, T cell proliferation and cytokine secretion . Costimulation is required for a productive immune response to occur. The lack of costimulation after engagement of T cell receptor by antigen results in a state of antigen specific unresponsiveness termed anergy. This places the costimulation pathway at a key location for controlling immune response. It also gives it a potential role in treatment of diseases such autoimmune diseases, organ rejection and tumour immunity . The B7 family of costimulatory ligands currently has two members, B7-1 (CD80) and B7-2 (CD86). Both B7-1 and B7-2 belong to the immunoglobulin gene superfamily . CD80 is a 55-kDa glycoprotein made up of 288 amino acids with transmembrane region and a short 19 amino acid cytoplasmic domain. Original article