On the left is a lymph node taken from a person during an ac…

On the left is a lymph node taken from a person during an active immune response. MZ = mantle zone; LZ = light zone and DZ = dark zone. This left image tissue is stained with H and E. The right image is from an adjacent tissue section stained by an anti-CD21 antibody. CD21 can be located on follicular dendritic cells or B cells. What type of T cell is most likely to be prominent in the same region as the region that stains with the anti-CD21 antibody?

Pathogenic Streptococcus pneumoniae possess a polysaccharide…

Pathogenic Streptococcus pneumoniae possess a polysaccharide capsule that prevents phagocytosis, allowing them to evade the immune system and multiple, causing pneumonia. S. pneumoniae that lack the capsule do not cause disease as they are readily destroyed by host phagocytes. When a mixture of living nonencapsulated and heat-killed encapsulated S. pneumoniae are injected into a mouse, the mouse dies, and living capsulated bacteria can subsequently be isolated from the mouse. Which of the following best explains this result?