Week 5 Discussion: Adaptive Immunity

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Required Resources

Read/review the following resources for this activity:

Initial Post Instructions

Your friend Bruce calls in a panic. He has just come from the doctor and been diagnosed with a bacterial infection. The doctor told him not to worry; his B cells will take care of it in no time! Knowing that you are studying the immune response, he is calling to ask you to explain this statement. Is the doctor correct? Is there more to the story?

Follow-Up Post Instructions

Respond to at least one peer or the instructor. Further the dialogue by providing more information and clarification.

Writing Requirements



Hello Professor and Class,

Yes, the doctor is correct. The bacterial antigens are first recognized by specific B cells. B cells then engulf the antigen and digest it into smaller fragments. These digested fragments are then displayed on the surface of B cells. Specific MHC molecules then bind to these antigen fragments on B cells. Specific mature T cells are then attracted to this antigen-MHC combination on B cells. This results in the secretion of cytokines by mature T cells which help in the multiplication and maturation of B cells into antibody producing plasma cells and memory B cells. Antibodies released into the blood by plasma cells react with specific bacterial antigens and result in the formation of antigen-antibody complexes that are either phagocytosed by macrophages or are cleared by the complement cascade system.

Another part of the immune system that plays a role in fighting pathogens are CD4 T helper cells.

According to Highleyman (2021), CD4, or helper, T cells coordinate the immune response. These are the primary targets of HIV. As the virus destroys CD4 cells, people become susceptible to opportunistic infections and cancers. Suppressing the virus with antiretroviral therapy protects CD4 cells, and monitoring CD4 counts—along with viral load—can show whether treatment is working.

CD8, or killer, T cells (also known as cytotoxic T cells) directly attack invaders. Unfortunately, killer T cells are usually not able to keep HIV in check without antiretrovirals.

After the immediate threat has been dealt with, a small number of memory B cells and T cells remain on guard, ready to fight the same invader again.

Answer 2:


Hi Professor Brener and class,

I would tell Bruce that yes, the doctor is correct. I would tell Bruce that B-cells are highly specialized defender cells that are tailored to different microorganisms. When our body is infected with a particular microbe, only the T- and B-cells that recognize it will respond. These selected cells then quickly multiply, creating an army of identical cells to fight the infection (Cowan, 2017). Special types of T- and B-cells ‘remember’ the invader, making you immune to a second attack. With the help of T-cells, B-cells make special Y-shaped proteins called antibodies. Antibodies stick to antigens on the surface of germs, stopping them in their tracks, creating clumps that alert your body to the presence of intruders (Petersone et al., 2018). Your body then starts to make toxic substances to fight them. Patrolling defender cells called phagocytes engulf and destroy antibody-covered intruders (Petersone et al., 2018).