lecture 03/07

Immune System Overview

• The immune system protects organisms from various pathogens, including bacteria and viruses.

• Understanding of immune system functions includes recognizing and responding to harmful agents.

Key Functions of the Immune System

• Detection of Pathogens: Essential for the immune response; must distinguish between self (not harmful) and non-self (harmful).

• Physical Blocking: Bodies utilize barriers to block pathogens from entering. E.g., cilia in airways help trap and eliminate pathogens.

Types of Immune Responses

Innate Immunity

• Definition: An immediate, non-specific response; reacts the same way regardless of the pathogen.

• Characteristics:

  • Built-in response systems (e.g., skin, mucous membranes)

  • Quick action upon pathogen detection; responds as the first line of defense (analogous to a smoke alarm for fire).

Acquired (Adaptive) Immunity

• Definition: A customized response based on previous exposure to specific pathogens.

• Characteristics:

  • Develops memory for pathogens, allowing for a more effective response in future encounters.

  • Adaptation of the immune response to specific pathogens rather than reacting the same way each time.

Pattern Recognition Receptors (PRRs)

• Function: Recognize common features shared by pathogen groups, such as fungal, bacterial, or viral characteristics.

• PRRs are present in both prokaryotes and eukaryotes, suggesting an early evolutionary mechanism to fight off pathogens.

Innate Immunity Functions

• Ready-Made Defense: Immediate physical barriers and immune cells are prepared to respond to any foreign threat without prior exposure.

• Types of Recognition: Innate immunity distinguishes between broad groups rather than specific pathogens, allowing for a rapid defensive action.

Examples of Immune Mechanisms

Toll-Like Receptors (TLRs)

• Role of TLRs: Function as PRRs; crucial for recognizing and responding to pathogens (e.g., fungal and bacterial pathogens).

• Signaling Pathway:

  • TLRs initiate signaling cascades upon recognition of pathogens, leading to the activation of immune responses.

  • TLRs trigger the expression of genes needed for antimicrobial responses.

Antigen Recognition

• Definition of Antigen: Any foreign molecule capable of eliciting an immune response, often synonymous with the pathogen signal.

• Mechanisms of recognition often involve specific receptor-ligand interactions that trigger immune responses.

Phosphorylation in Immune Response

• Pele Kinase: Enzyme involved in the immune signaling pathways; phosphorylates key proteins such as dorsal and cactus.

• Mechanism of Action:

  • Phosphorylation alters protein conformation, potentially affecting their interactions and activity.

  • Phosphorylated dorsal may be transported to the nucleus, leading to activation of antifungal response genes.

• Understanding phosphorylation helps to elucidate how external signals are converted into cellular responses, a fundamental concept in cell signaling.

Conclusion

• The immune system's function relies on its ability to quickly detect pathogens and adaptively respond to them.

• Various cellular pathways and mechanisms, including innate and acquired responses, working together characterize the complexity of immune responses.