the ancient observation that someone who had recovered from the plague could safely care for those newly diseased

inflammatory response

injection of antibodies to the toxin

body cell becomes infected with a virus → new viral proteins appear → class I MHC molecule-antigen complex displayed on cell surface

only II and III

a condition in which self molecules are treated as non-self

passive immunity

short-lived plasma cells that secrete antibodies for the antigen

blocking the attachment of the IgE antibodies to the mast cells

innate immunity

mast cells and histamines

I, II, and III

a group of antimicrobial proteins that act together in a cascade fashion

there are some epitopes (antigenic determinants) common to both pox viruses

MHC molecules of the donor may stimulate rejection of the graft tissue, but bacteria lack MHC molecules

You had an adaptive immunity to that virus.