Medical Definition of M protein
1 : an antigenic protein of Group A streptococci that is found on the cell wall extending into the surrounding capsule, is variable among the different serotypes, and confers streptococcal virulence by protecting the cell from phagocytotic action
— called also M substance
2 : a monoclonal antibody that is produced by plasma cells abnormally proliferating from a single clone and that is characteristic of monoclonal gammopathy
an act or instance of returning to life
Get Word of the Day daily email!
Love words? Need even more definitions?Merriam-Webster unabridged
Words at Play
Ask the Editors
- On Contractions of Multiple Words
- A Look at Uncommon Onomatopoeia
- Is Singular 'They' a Better Choice?
- Words from Greek and Latin Quiz Take the quiz
- Name That Thing: Animal Edition Take the quiz
- Name That Thing Take the quiz
- Add Diction Play the game