Antigenic groups identified by different sets of antibodies reacting in a similar manner to standard cell lines are best described by

Antigenic groups identified by different sets of antibodies reacting in a similar manner to standard cell lines are best described by

• A. cytokines
• B. opsonins
• C. neutrophilic granules
• D. clusters of differentiation

Answer: (D)

Understanding how immune cells are labeled by the proteins on their surface helps explain this concept. When a variety of monoclonal antibodies are tested against standard cell lines, certain patterns of reactivity define specific sets of surface antigens. Those patterns are grouped into clusters of differentiation, or CD markers, which are used to identify and distinguish different cell types (for example, CD4 on helper T cells, CD8 on cytotoxic T cells, CD19 on B cells, CD14 on monocytes). The other options describe different roles in immunity—cytokines are signaling molecules, opsonins tag pathogens for phagocytosis, and neutrophilic granules contain antimicrobial substances—but they do not describe a standardized system of cell-surface antigen groups defined by antibody reactivity.

Understanding how immune cells are labeled by the proteins on their surface helps explain this concept. When a variety of monoclonal antibodies are tested against standard cell lines, certain patterns of reactivity define specific sets of surface antigens. Those patterns are grouped into clusters of differentiation, or CD markers, which are used to identify and distinguish different cell types (for example, CD4 on helper T cells, CD8 on cytotoxic T cells, CD19 on B cells, CD14 on monocytes). The other options describe different roles in immunity—cytokines are signaling molecules, opsonins tag pathogens for phagocytosis, and neutrophilic granules contain antimicrobial substances—but they do not describe a standardized system of cell-surface antigen groups defined by antibody reactivity.