CD86 is a well-known costimulatory molecule in its interaction with CD28 and/or CTLA present on T cells, and is essential for full activation of naive T-cell and subsequent differentiation. Usually, the B7 molecules are expressed mainly on APCs and B cells and in specific conditions on other activated cells. These costimulatory molecules are involved in the development of allergic inflammation and airways hyperreactivity (AHR) in allergen-challenged mice. Activated T cells, CD4+CD25+, express CD86 in the first 60 minutes after the specific inhalation exposure. These T cells can be relevant in IgE mediated allergic reaction possibly by an autocrine co-stimulation via CD28/CTLA activation pathway. The blockage of the expression of CD86 could be a potential therapeutical target to reduce the magnitude or the progression of the allergic reaction.