Which white blood cell is described as alerting the body to invasion?

• A. Basophil
• B. Lymphocyte
• C. Erythrocyte
• D. Platelet

Answer: (A)

An initial alert to invasion comes from cells that release chemical signals to kickstart inflammation. Basophils are white blood cells that release histamine and other mediators when tissue is invaded. Histamine increases blood vessel permeability and promotes inflammation, helping bring in more immune cells to the site and signaling that there’s a threat. That signaling role is why basophils are described as alerting the body to invasion. Lymphocytes are involved in a later, targeted immune response; erythrocytes carry oxygen; platelets are mainly for clotting and wound repair rather than signaling an invasion.