Medical Definition of accessory cell
: any of various cells in addition to the T cells and B cells that help to generate an immune response; specifically : antigen-presenting cell T lymphocytes cannot recognize free antigen but are dependent on antigen presentation by accessory cells.—Adriano Fontana et al., Nature, 19 Jan. 1984
Seen and Heard
What made you want to look up accessory cell? Please tell us where you read or heard it (including the quote, if possible).