Ted’s Review Session

Overview of Cell Signaling and Immune Response

• Cells signal the immune system about their health status:

  • Normal, abnormal, or needing destruction.

  • MHC (Major Histocompatibility Complex) proteins play a key role in this signaling.

Antigen Presentation

• MHC Class II Proteins:

  • Present antigens from outside the cell.

  • Involvement of Antigen Presenting Cells (APCs) like macrophages:

    • Perform phagocytosis to ingest the antigen.

    • Digest the antigen and present it using MHC Class II to T helper cells.

    • Secrete cytokines to activate T helper cells.

• MHC Class I Proteins:

  • Present antigens from infected or abnormal cells to cytotoxic T cells.

  • Essential for T helper cells to recognize antigens.

B Cells and Antigen Recognition

• B cells can recognize antigens independently and also function as antigen presenting cells for T helper cells.

• Significance of MHC:

  • MHC proteins are crucial for distinguishing self from non-self; their dysfunction can impair antigen recognition.

Membrane Structure and Drug Targeting

• Cell membranes must stabilize using sterols:

  • Eukaryotic cells utilize cholesterol; prokaryotic cells do not.

• Unique cell structures (e.g., ribosomes, cell walls) serve as targets for antibiotics:

  • Antibiotics can specifically target structures unique to prokaryotes, thus sparing eukaryotic cells (e.g., antibiotics targeting 70s ribosomes).

Endospores Survival Mechanism

• Endospores are a survival strategy for bacteria in unfavorable conditions:

  • They are formed as a copy of DNA encased in a tough shell when conditions deteriorate.

  • Can survive for tens of thousands of years and become metabolically inactive until favorable conditions return.

  • Example: Clostridium endospores can lead to conditions like tetanus when they germinate in wounds.

Protozoa Characteristics

• Protozoa are aquatic organisms without cell walls, making them fragile:

  • Exist as trophozoites (active form) or cysts (dormant form).

  • Movement methods include flagella, cilia, or amoeboid movement.

Cytosol and Prokaryotic Features

• Prokaryotic cells always have certain structures like:

  • Peptidoglycan cell walls

  • Lipopolysaccharide in Gram-negative bacteria, a trigger for immune responses.

Immune Response Dynamics

• The immune system recognizes danger patterns (e.g., peptidoglycan, lipopolysaccharides):

  • Overstimulation can lead to excessive immune responses, which may be harmful to the host.

Bacteria Diversity and Genetic Transfer

• Binary fission is the primary reproduction method in bacteria but lacks genetic diversity:

  • Conjugation allows for genetic exchange between cells improving survival under selective pressure (e.g., antibiotic resistance).

Antibody and Cytokine Interactions

• Cytokines from T helper cells instruct immune cells to activate, divide, or differentiate:

  • Regulation of immune response based on the threat level.

• Antibodies interact with pathogens, blocking infections before they occur.

Microscopy Techniques

• Different microscopy methods have their respective applications:

  • Bright field for general use.

  • Dark field, phase contrast, fluorescence, and electron microscopy for specialized observations of various microbial structures.