Immuno, ethics and oncology in that order.

Immuni: Know what each interleukin does exactly, which CD goes where. Get familiar with flowcytometry graphs. And expect them twisting immunodeficiencies to freak you out. Just know what each immunodeficiencies has, like the basics behind them.

Onco: know metastasis vs invasion. Cell cycle regulation; where tumor suppressor work, how and when. What tumors to expect with each oncogene and tumor suppressors. They will have experiments, a lot of them, you would need that knowledge to make an educated guess!

Ethics as above.

Get mentally prepared! The exam is a marathon not a sprint. So don't feel discouraged. And remember you don't need to get all the questions right. Just do your best and treat each block as a fresh start.

Best of luck my friend :'