The present invention provides a method for polyclonal stimulation of T cells, the method comprising contacting a population of T cells with a nanomatrix, the nanomatrix comprising a) a matrix of mobile polymer chains, and b) attached to said matrix of mobile polymer chains one or more stimulatory agents which provide activation signals to the T cells; thereby activating and inducing the T cells to proliferate; wherein the nanomatrix is 1 to 500 nm in size. At least one first and one second stimulatory agents are attached to the same or to separate mobile matrices. If the stimulatory agents are attached to separate nanomatrices, fine-tuning of nanomatrices for the stimulation of the T cells is possible. Closed cell culture systems also benefit from this method.