Could you correct my English?

My Job

When I was working in Japan, I worked was at a Japanese pharmaceutical company as a research scientist. Actually I'm Still am a member of that, but since I was sent to study at a Rome university in Rome by my company, I'm became/regressed into/ a ph.D student now. I was [can't use past tense because then it implies you are doing something different] am to researching to in developing a new diagnostic product to be used/implemented in Japan. MHC (Major Histocompatibility Complex, (MHC) is expressed on found in almost all human cells and they functions in the immunity system. Because the "type" of Since each MHC is different from person to person, it could be a main reason for the rejection after organ rejecting after transplant or something. Therefore it is necessary to check the "type" of the MHC in a patient before the treatment. It is like blood type checking before transfusion. [put some common analogy so that the layman can understand better] I was am to developing the a product to for this kind of check it. When I left Before leaving Japan, the project was in progress. Recently Lately, my previous boss told me that they finally made it it was done and would be putting it on the market. He I was asked me that if they could use my the initials of my name as for the name of the product! I Of course said it was a resounding yes from me!. Although the way to produce it was very the production is extremely difficult, tough, nevertheless, I'm very happy to hear the news.

Wow!  Congratulations.  Didn't know you are such a smart cookie :)  Thank you for helping in allevating the pain and suffering of mankind.

When I was in Japan, I worked at a Japanese pharmaceutical company as a research scientist. Actually I'm still a member of that, but since I was sent to study at Rome University by my company, I'm a ph.D student now. I was researching developing a new diagnostic product in Japan. MHC, major histocompatibility complex, is expressed on/seen in almost all human cells and functions in the immune system. Because the "type" of MHC is different from person to person, it could be a main reason for the rejection after organ transplant or something. It is necessary to check the "type" of the MHC before the treatment. I was developing the product to check it/the type. When I left Japan, the project was in progress. Recently, my previous boss told me that they finally made it and would put it on the market. He asked me if they could use my initial for the name of the product, I, of course, said yes. Although producing it was very tough, I'm very happy to hear the news.

I wasn't sure if "expressed on" is a techinical scientific term or not so I just put what sounded more natural to me. 

That's amazing though, congratulations! :)