Which type of white blood cells are involved in graft-versus-host disease (GVHD)?

Graft-versus-host disease (GVHD) occurs when donor immune cells mount an immune response against the recipient's tissues, typically following a stem cell or organ transplant. In this context, lymphocytes, specifically T cells, play a pivotal role.

Lymphocytes include subtypes such as T cells, which are crucial in recognizing foreign tissues. When donor T cells recognize the recipient's cells as foreign due to differences in major histocompatibility complex (MHC) markers, they become activated and lead to inflammation and tissue damage, characterizing GVHD.

In contrast, neutrophils are primarily involved in the innate immune response and do not have the same role in recognizing foreign grafts. Monocytes can differentiate into macrophages and have their function, but they do not directly cause GVHD. Eosinophils are associated more with allergic responses and parasitic infections rather than with the immune mechanisms underlying GVHD.

Thus, lymphocytes are the key players in the pathophysiology of graft-versus-host disease, making them the correct choice.