Entering streptococcal research
Lancefield joined the Rockefeller Institute in 1918 and began studying haemolytic streptococci. Building on serological approaches used by Avery and others for pneumococci, she applied antigen–antibody reactions to distinguish streptococcal populations.
References: [1]
Carbohydrate antigens and groups
She classified streptococci into groups according to differences in carbohydrate antigens. Labels such as group A and group B supplied a common serological framework for comparing strains and investigating their associations with infection.
References: [1]
M protein within group A
Within group A, she further analysed the cell-surface M protein and distinguished serotypes through antigenic variation. Carbohydrate grouping and M-protein typing represented different levels of classification. Her work also clarified relationships between bacterial surface components and host immune responses.
References: [1]