Immunology 11: Th1 & Th2 Cells and Their Relevance to Cell-Mediated & Humoral Responses

Question 1

Major problem in analyzing properties and functions of lymphocytes?

Answer 1

lymphocyte with a specific function is extremely rare

→ ex, T cell specific for an antigen appears 1/100 000 spleen cells – multiplies/clones when precursor cell induced

Question 2

Way to get around lymphocyte problem?

Answer 2

stimulate precursor cell in presence of certain growth hormone for T cells, IL2 to give rise to clones of T cell
→ IL2 is a cytokine

Question 3

Cytokines

Answer 3

molecules secreted from T cell clones (active) that go to their appropriate target cells by the producing cell binding to the target cell with its receptor
→ either positively or negatively regulate growth and differentiation of other cells (including other T cells) to which they are delivered
→ different T cells secrete different cytokines upon stimulation

Question 4

2 major types of CD4+ T cells (spleen)

Answer 4

→ Th1 - produce IL2 and IFNg

→ Th2 - produce IL4 and IL10

Question 5

IL2

Answer 5

growth factor for all T cells

→ important for it to be produced by Th1 cells

Question 6

IFNg

Answer 6

→ prevent viral multiplication and its delivery to infected macrophages by pathogen-specific CD4 T cells that result in macrophage activation
→ favors development of Th1 (cell-mediated) responses

Question 7

Macrophage activation

Answer 7

inc in metabolic pathways toxic for most pathogens inside cell
→ referred to by immunologists as angry

Question 8

Th1 cells

Answer 8

→ secrete IL2 and IFNg, as well as mediate DHT

→ these functions suggest central role for Th1 cells is cell-mediated immunity

Question 9

CD8+ T cells

Answer 9

generated upon viral infection
→ often deliver IFNg to virus-infected cells
→ are cytotoxic for virus-infected cells

Question 10

IL4 and IL10

Answer 10

→ made by Th2 cells
→ central role in humoral immunity: favors induction of humoral (Th2) responses
→ inc in IL4 = inc IgG and IgE responses

Question 11

Levels of IFNg and IL4 regulate ____.

Answer 11

→ exclusivity between cell-mediated (Th1) responses and antibody (Th2) responses
→ IFNg = Th1 response
→ IL4 = Th2 response

Probably involved in inhibiting induction of opposing class

Question 12

How can you prevent a cell-mediated, Th1, response using this information?

Answer 12

→ give animal, at time of infection, antibodies to bind to and inactivate IFNg, and a Th2 response (humoral/antibody) will occur instead
→ vice versa, give animal antibodies that bind to and inactivate IL4, and a Th1 response will occur