Plasma cells arise from B-lymphocytes. When a B-lymphocyte's antibody comes in contact with a matching antigen presented by a macrophage, the B-lymphocyte will differentiate into a plasma cell. The plasma cell will then release free antibodies into the blood which can then attach to the pathogens.

Memory B-cells remain latent in the body and differentiate into plasma cells upon reinfection by the same antigen. Neutrophils, macrophages, and monocytes have phagocytic properties that allow them to engulf and digest pathogens. Mast cells and basophils secrete histamine to stimulate the inflammatory response. Dendritic cells and some other cell types can present antigens to helper T-cells to initiate an adaptive immune response.

Lymphocytes are cells of the adaptive immune system that are mainly found in the lymph. They include the T cells, B cells, and natural killer cells. Macrophages and dendritic cells are types of phagocytes. Basophils and eosinophils are granulocytes. Neutrophils are considered both a granulocyte and phagocyte. 

Antibodies are glycoproteins that are secreted by B cells. B cells must be activated by exposure to a specific antigen before they are able to produce antibodies against the antigen it was exposed to. This is part of the adaptive immune system. 

Autoimmune diseases result when the body attacks its own cells. Regulatory T cells work to suppress the body's lymphocytes that may react to self antigens. When regulatory T cells are not working properly, lymphocytes that may react with self antigens are able to cause damage and lead to autoimmune disease. 

Tissues of the immune system are classified as central (primary) or peripheral (secondary). Primary tissues include bone marrow and the thymus. Within the bone marrow, B and T cells are generated and B cells mature. In the thymus T cell maturation occurs.

Tissues of the immune system are classified as central (primary) or peripheral (secondary). Primary tissues include bone marrow and the thymus. Within the bone marrow B and T cells are generated; B cells also mature here, Whereas T cell maturation occurs in the thymus. 

The adaptive immune system consists of the humoral and cell mediated branches. Humoral immunity protects against extracellular pathogens, while the cell-mediated pathway protects against intracellular pathogens. Cells of the cell mediated branch include T helper cells (CD4+: these cells help B cells and other cells activate so they can do their job) and cytotoxic T cells (CD8+: which directly kill infected host cells). Antibodies are not cells.

Tissues of the immune system are classified as central (primary) or peripheral (secondary). Primary tissues include bone marrow and the thymus. Within the bone marrow, B and T cells are generated and B cells also mature. T cell maturation occurs in the thymus. 

Normally, eosinophils are not produced in high quantities in the body except in the face of parasitic infection. They typically constitute only 2% of the total white blood cell count. Eosinophils are classically elevated in response to infection from a parasite. The other cell lines in the answer choices would not be elevated due to a parasitic infection.

IFN-gamma is the main chemokine produced by CD4 T-cells to promote the oxidative killing of phagocytosed organisms in macrophages. Without IFN-gamma, macrophages can still ingest pathogens, though their killing efficiency will be far reduced.