Natural killer cellsa. are known for attacking large parasites, such as tapeworms.b. engulf pathogens and present antigens to T cells.c. recognize the absence of MHC-I molecules on a cell surface.d. produce antibodies.

Helper T cells can be activated by macrophages(which engulf everything indiscriminately) or by B cells (which only engulf antigens that stick to their receptors).  A. What properties so macrophages and B cells have ibn common that allows them both to activate T cells? B. It has been suggested that macrophages probably do most to fhte T cell activating in the primary response but B cells do most of it in the secondary response. Why does this make sense?

Which of the following best describes the impacts of antigenic variation? Mark all that apply.    A. requires clonal selection of B cells   B. causes a primary immune response   C. involves T-independent immune responses    D. memory cells are stimulated by the antigen variants

A. Organism that causes diseaseB. Larger in children than adults, this organ is the site of T cell maturation.C. Small region of substance or organism that binds directly to antibody.D. With granules that take up acidic stains, these white blood cells defend against parasites.E. Star-shaped cells critical for T-cell activationF. One type of complement pathwayG. These molecules "show off' self or non-self-peptides to T cells.H. A protein fragment that tags cells for destruction by phagocytesI.Substance or organism that induces an immune response.I.May be released into circulation or serve as a B cell receptor.K. Signalling molecule made by virally infected cells.L. The most abundant white cells in the blood, these phagocytic cells have multilobed nucleiM. A laboratory procedure that can test for antigen or antibody.N. A remarkable intracellular complex that amplifies the innate immune responseO. Receptors that recognize pathogen products and cause macrophages to produceinterleukins.P. A…