Lancefield grouping of streptococci is done by using-
β hemolytic Streptococcus is classified to group A-V based on C carbohydrate antigen (Lancefield classification)
M protein is used to further classify group A Streptococcus (Griffith typing).

Ref: Apurba Sastry’s Essentials of Medical Microbiology 1/e p221, Ananthanarayan 9/e p209
M Protein
Group C peptidoglycan cell wall
Group C carbohydrate antigen
Staining properties