Cellular Immunity

Question 1

▪ Antigen-presenting cells (APCs), such as dendritic cells, macrophages, and B cells, engulf
and process antigens (pieces of pathogens).
▪ These APCs present antigen fragments on their cell surface using major histocompatibility
complex (MHC) molecules.

Answer 1

Antigen Recognition

Question 2

▪ Helper T cells (CD4+ T cells) recognize antigens presented by APCs through their T cell receptors (TCRs).
▪ Co-stimulatory signals, such as CD28 on T cells interacting with CD80/86 on APCs, are required for full T cell activation.
▪ Interleukin-1 (IL-1) and other cytokines also play a role in _________

Answer 2

T Cell Activation

Question 3

▪ Once activated, helper T cells undergo _________, leading to the proliferation of a large number of identical T cells specific to the presented antigen.

Answer 3

Clonal Expansion

Question 4

▪ Helper T cells differentiate into specialized subsets, such as Th1, Th2, Th17, or regulatory T cells (Tregs), depending on the cytokine environment.
▪ Th1 cells are involved in cellular immunity and activation of cytotoxic T cells

Answer 4

Differentiation of Helper T Cells

Question 5

▪ Cytotoxic T cells (CD8+ T cells) recognize antigens presented on infected cells’ MHC class I molecules.
▪ Interleukin-2 (IL-2) and other cytokines produced by helper T cells stimulate the activation and differentiation of cytotoxic T cells

Answer 5

Activation of Cytotoxic T Cells

Question 6

Activated cytotoxic T cells release perforin and granzymes, inducing apoptosis (programmed cell death) in the infected cells

Answer 6

Cytotoxic Activity

Question 7

▪ Some activated T cells differentiate into memory T cells, providing long-term immunity
against the specific pathogen.
▪ Memory T cells respond more rapidly and efficiently upon re-exposure to the same antigen.

Answer 7

Memory T Cells

Question 8

Tregs suppress excessive immune responses to prevent autoimmune reactions and maintain immune system balance

Answer 8

Regulation by Regulatory T Cells (Tregs)

Question 9

▪ After the infection is cleared, most effector T cells undergo apoptosis.
▪ Memory T cells persist, providing rapid and enhanced responses upon subsequent encounters with the same pathogen

Answer 9

Resolution and Memory

Question 10

_________ protects the body against intracellular threats and works in concert with _________ to provide a comprehensive defense against a wide range of pathogens

Answer 10

Cellular immunity, humoral immunity