Cell-Mediated (Cellular) Immunity [aka T-cell immunity] - Physiology & Immunology

Summary

In this educational video, Medicosis dives deep into the intricacies of the immune system, focusing on cellular immunity driven by T lymphocytes. The script explains the roles of B lymphocytes in defending against bacteria and T lymphocytes in combating viruses and fungi. It explores the communication between immune cells via cytokines, the significance of MHC in T cell activation, and the importance of recognizing self from non-self to prevent autoimmune diseases. The video also touches on the challenges of organ transplants, the prevention of organ rejection, and the complications of hemolysis, offering a comprehensive overview of immunology.

Takeaways

• 🔬 B lymphocytes mainly defend against bacteria, while T lymphocytes defend against viruses and fungi.
• 🦠 Plasma cells, derived from B lymphocytes, secrete antibodies which neutralize antigens and activate various immune responses.
• 🧪 There are three complement pathways: classical, alternative, and mannose-binding lectin.
• 🧬 Cytokines, such as interleukins, colony-stimulating factors, and tumor necrosis factor, help immune cells communicate.
• 🔗 Antigen-presenting cells present antigens to lymphocytes, which then activate B and T lymphocytes.
• ⚔️ T helper cells (CD4) assist other immune cells, while T cytotoxic cells (CD8) directly kill infected or cancerous cells.
• 🔄 Major Histocompatibility Complex (MHC) molecules present antigens to T cells; MHC class I activates CD8 cells and MHC class II activates CD4 cells.
• 🧠 Immunodeficiency, such as AIDS caused by HIV, weakens the immune system by attacking CD4 cells.
• 🤰 The placenta acts as a barrier between mother and fetus, preventing maternal immune attack on the fetus.
• 🩸 Successful tissue or organ transplants require matching donor and recipient MHC and immunosuppressive therapy to prevent rejection.

Q & A

What is the main difference between humoral immunity and cell-mediated immunity?

Humoral immunity, primarily mediated by B lymphocytes, defends the body against bacteria through the secretion of antibodies in the body's fluids, while cell-mediated immunity, primarily mediated by T lymphocytes, involves direct cell-to-cell interactions to destroy infected cells, such as those affected by viruses, fungi, or cancer.

What are the three types of cytokines mentioned in the script?

The three types of cytokines mentioned are interleukins, colony-stimulating factors (CSF), and tumor necrosis factor (TNF).

How do antigen-presenting cells (APCs) interact with T lymphocytes?

APCs interact with T lymphocytes by presenting antigens on their surface using major histocompatibility complex (MHC) molecules. MHC class I is used for activating CD8 T cells, while MHC class II is used for activating CD4 T cells.

What is the role of T helper cells in the immune response?

T helper cells play a crucial role in activating other immune cells, such as B lymphocytes, to produce antibodies or become memory cells, enhancing the immune response to subsequent exposures to the same antigen.

How does the immune system distinguish between self and non-self?

The immune system distinguishes between self and non-self through several mechanisms, including energy depletion to weaken potentially harmful self-reactive lymphocytes, deletion of strongly self-reactive T cells during maturation in the thymus, and the action of T regulatory cells that suppress self-reactive immunity.

What is the significance of the term 'humoral' in humoral immunity?

The term 'humoral' in humoral immunity refers to the fact that antibodies are secreted into the body's fluids, such as serum or mucous membranes, to combat pathogens.

What is Acquired Immunodeficiency Syndrome (AIDS) and what causes it?

AIDS is a syndrome characterized by a weakened immune system due to the infection with the Human Immunodeficiency Virus (HIV), which is an RNA virus. HIV-1 is the more common and global type, which primarily attacks CD4 helper T lymphocytes, impairing the immune system's ability to fight infections and diseases.

What is the role of Human Leukocyte Antigen G (HLA-G) in pregnancy?

HLA-G, unique to pregnancy, is secreted by the placenta and helps prevent the mother's immune system from attacking the fetus by inducing a state of immunodeficiency that is protective for the survival of the fetus.

Why are live attenuated vaccines not recommended for pregnant women?

Live attenuated vaccines are not recommended for pregnant women because their immune systems are already in a state of immunodeficiency to protect the fetus. The live microorganisms in these vaccines could pose a risk to both the mother and the developing baby.

What are the complications of hemolysis after a blood transfusion?

Complications of hemolysis include hyperkalemia, hyperphosphatemia, and kidney damage due to the release of potassium, phosphate, and hemoglobin from burst red blood cells. Hemoglobin can also cause kidney failure and hemosiderin in the urine.

How can organ rejection after a transplant be prevented?

Organ rejection can be prevented by matching the donor and recipient for blood and HLA types before surgery, and by using immunosuppressants after surgery to suppress the recipient's immune system and prevent it from attacking the transplanted organ.