It is a practice-related complaint. It's usually caused by nurses or doctors not taking precautionary measures and making sure that their hands are cleaned and that they wear masks when operating on someone or assisting in an operation. It could also be unclean untensils that are used for surgery too!
Don't know if you typed this too fast spelt something wrong, so I'm not sure, sorry.
All t cells originate from haematopoietic stem cells in the bone marrow