which antigen presenting cells, MQ, DC?, a standard protocol are available at protocol online. However, after irradiation they still live and present for 3-5 days, then die.
you need to know if the irradiation affected APC and they may become mutated since effects of irradiation are dose and type dependent. I have an article published about the effect of irradiation on Neutrophils , may help you...regards
You could consider fixing the APCs after irradiation, but before adding the T cells. They will not die, but are still able to present/stimulate with what is on their surface at the time of fixing.