What is the white blood cell called that participates in the specific immune response? antigens antibodies macrophages pathogens

I think it is called antigens

Blood transfusions were rarely done and often fatal; they were outlawed until the nineteenth century.

Bmust be the answer, as technically all organs move, so a is incorrect. all organs are made of different types of cells, so that isn’t a problem, so c is also incorrect. human hearts are very similar to many other animals’ hearts, so d is also incorrect, yet the heart is made of muscle, which is hard to grow in the lab so it would be correct to say b