stimulating lymphocyte culture---HELP - PHA-M or PHA-L (Jul/10/2007 )

I am setting up micronuclei assay (cytokinesis-block micronucleus [CBMN]assay) and the protocol uses PHA but I dont which one.....is it PHA-M or PHA-L. Which is the best one for stimulating lymphocytes????

PHA-L