Abstract: Objective: To study the effect of anti-CD3 CD28 on enhancing lymphocyte transform function（LTF）,in order to understand and evaluate characteristics of anti-CD3/28 to expand T lymphocytes in PBMC and affection of the APC amount to T cells expanding.Methods: with the methods of incorporation of ~3H-thymidine(³H-TdR) for measure LTF,cell culture and flow cytometry（FCM）,using coated anti-CD3 and anti-CD28 to stimulate T lymphocytes.Then raised the antigen presentation cell（APC） concentration,measured the LTF with normal APC concentration group of anti-CD3 alone as control.SI and CD8⁺CD25⁺cells′percentage was used to evaluate all factors to LTF.Results: anti-CD3 can enhance LTF in normal APC grounp and anti-CD28 has co-stimulation function.In no APC group,the LTF of anti-CD3 came down sharply,but anti-CD28 also had co-stimulation function.In four times APC group,anti-CD3 can enhance LTF in normal APC grounp more and anti-CD28 had no co-stimulation function.Only anti-CD28 had no effective activity.The result of FCM was parallel with the SI.Conclusion: anti-CD3 and anti-CD28 can mimic first and second signal to active T cells,while anti-CD28 may replace second signal function which offered by APC.But APC also has other function to affect lymphocytes activity.lymphocyte transformation;flow cytometry;antigen-presenting cells