is there a specific reason you are choosing not to use readily-available commercial antibodies? (for instance: https://atlasantibodies.com/#!/products/ACVR2A-antibody-HPA046997)

I agree with Jessica. There are different methods of immunization in animals, but trying to establish them on your own can be frustrating. Besides, you need to meet the legal requirements of your country for manipulating animals. You can save a lot of time, money and get better results if you send your protein sample to a commercial antibody service. They will handle your request with already optimized methods and will even offer you some minimum guarantee about the outcome.

Please do not forget to screen - and collect - pre-immunization serum.

From Rat ?? or anti-Rat- ACVR2A-Ab

If you've your protein already expressed- it's easy. you can also use mouse, guinea-pig or even rabbits depending on how much antibody you require. Let me know your choice and I can provide you a detailed protocol as we do it often for our work.

i have rats. i expressed gene of ACVR2A. i have expression vector clones and primary cell culture proteins. 

You should have purified protein for immunization purposes - otherwise you may end up with antibodies mainly against cellular proteins. I believe you're looking for polyclonal antibodies?

@ Mana Mahapatra

Could you please send me the detailed protocol for raising poly-clonal antibody against a purified recombinant protein in RAT (sprague dawley). Previously we have generated polyclonal antibody in rabbits and mouse but we have no experience with rat.