1. Cytokines are small proteins that transfer information within the immune system. List the actions of cytokines given in this Topic:
a.
b.
c.
d.
e.
2. Interleukin 1, a cytokine, acts as a chemical alarm to alert the immune system to the presence of a pathogen. List the three actions given for interleukin 1 in this Topic:
1. _________________________
2. _________________________
3. _________________________
3. Interleukin 2, released by helper T cells, causes proliferation of activated lymphocytes. This process is called _________________________.
4. The two major classes of lymphocytes that mediate cellular immunity are based on the presence of surface proteins called _______ proteins. The most common are those with the _______ markers.
5. Below are the two major classes of cells with CD protein markers. List what the cells become and what class of MHC proteins they bind.
CD4 cells: Most become _____________ cells but some become _____________ cells
Bind to ______________ MHC proteins
CD8 cells: All become ______________ cells
Bind to ______________ MHC proteins
6. The HIV virus binds to CD4 surface proteins and destroys the ______________ cells.
7. The _______ proteins are one major class of self-antigens. Thus, before an organ transplant, the donor’s and the recipient’s ________ proteins are matched as closely as possible to decrease the chance of organ _______________.
8. ______________ cells circulate through the body searching for infected or cancerous cells by examining the antigenic determinant on ______________ MHC proteins on the cell surface. Fragments of ______________, degraded proteins are loaded onto these proteins in the endoplasmic reticulum. If the antigenic peptide is a/an ______________ antigen, the body cell will be destroyed.
9. Unlike class I MHC proteins, which can be displayed on any nucleated cell, class II MHC proteins are displayed only on select cells. Name the antigen-presenting cells that have class II MHC proteins:
a. _________________________
b. _________________________
c. _________________________
These cells communicate with CD4 cells, which will become ______________ cells. Antigens presented on class II cells are ______________ antigens.
10. Class II MHCs are produced in the _________________________ and pick up the exogenous antigens when they fuse with the ______________.
11. Name two results of presenting the exogenous antigen on class II MHC proteins:
1. CD4 cells are converted to helper T cells when ______________ cells and ______________ present the antigen.
2. ______________ cells and ______________ present antigens to helper T cells to request further activation.
12. Dendritic cells are responsible for activating most T cells. Choose the correct answer for each of the following:
They can capture antigens found ______________ (extracellularly, intracellularly, or both extra- and intracellularly).
They can activate ______________ (CD4, CD8, or both CD4 and CD8) cells.
They can express ______________ (MHC I, MHC II, or both MHC I and MHC II) proteins.
13. Exception: Normally, when cells express endogenous foreign antigens on class I MHC proteins on their cell membrane, they are marked for destruction. This is not true for ______________ cells. On these cells the presentation acts as an activation signal for ______________ cells.
14. List the two steps necessary for T cell activation:
1.
2.
15. Once T cells are activated they undergo proliferation (called ____________ __________________) and differentiation. ______________, a type of cytokine, is necessary for the proliferation.
16. Antigen-presenting cells will express co-stimulatory molecules when they have been signaled by the ______________ defense mechanisms that an infection is present. However, if there is no infection, the antigens on the MHC protein are likely to be ______________. Thus, without co-stimulation, the T cells become inactivated, a process called ______________.
17. There are two ways to induce a process of self-destruction in a cell, which is called ______________:
1. Cytotoxic T cells look for the presence of MHCs with foreign antigens and release ______________ and ______________ or they bind to a/an ______________ ______________ receptor (Fas receptor) on the surface of the cell.
2. Natural killer cells look for the absence of ______________ and are thus able to eliminate abnormal cells that cytotoxic T cells cannot detect.
18. Helper T cells are critical for the activation of ______________ and ______________ T cells.
19. The helper T cell can help activate the CD8 cell to become a/an ______________ T cell in two ways:
1. It stimulates the dendritic cells to express additional ______________ molecules.
2. It secretes ______________ (including interleukin 2) to help activation.
20. TH1 cells secrete ______________ interferons, which increase the effectiveness of ______________ and ______________ T cells. TH2 cells secrete interleukins _______ and _______, which promote activation of _____ cells.
21. Regulatory T cells suppress the activity of other T cells by direct ____________________ contact or by releasing ____________________. They are important in helping to prevent ___________________ diseases.