Sistema inmunitario

Overview of the Immune System

Introduction to the Immune System

• The immune system is a fascinating body system that works continuously to protect against pathogens, which include viruses, bacteria, fungi, and parasites.

First Line of Defense

• The body's first line of defense includes external protections like skin and mucous membranes (e.g., nasal lining) that prevent pathogen entry. This defense is non-specific and does not selectively block pathogens.

Second Line of Defense: Inflammatory Response

• When pathogens breach the first line, the inflammatory response kicks in. For example, stepping on a sharp object can activate mast cells that release histamine, causing blood vessels to dilate and become more permeable. This allows white blood cells like macrophages to reach the injury site more easily.

Role of Complement System

• The complement system aids the immune response by attracting more macrophages to consume pathogens when activated during an inflammatory response. This process helps eliminate threats effectively but remains non-specific as it does not identify specific pathogens.

Third Line of Defense: Adaptive Immunity

• If initial defenses fail, adaptive immunity targets specific antigens associated with pathogens. This complex response involves T-cells and B-cells tailored to recognize unique features of invaders. Understanding this layer requires deeper exploration beyond basic concepts presented here.

Mechanisms of Adaptive Immunity

Cell-Mediated Immunity

• Cell-mediated immunity involves cytotoxic T-cells that destroy infected cells through apoptosis triggered by signals from infected cells presenting antigens on their surface. These T-cells use perforin proteins to create holes in infected cell membranes leading to cell death.

Activation Process for Cytotoxic T-cells

• To activate cytotoxic T-cells, an infected cell must present a pathogen's antigen on its membrane as a signal for destruction; alternatively, macrophages can process and present these antigens to helper T-cells which then stimulate cytotoxic T-cell activity further amplifying the immune response.

Helper T-cell Functionality

• Helper T-cells play a crucial role in both cell-mediated and humoral responses by releasing chemical signals after binding with antigen-presenting cells (like macrophages), thereby enhancing overall immune function against infections or diseases encountered by the body.

Understanding Antibodies and Immune Response

The Role of White Blood Cells and Antibodies

• The discussion begins with the stimulation of a white blood cell known as B cells, which have the ability to produce antibodies.

• Antibodies are distinct from antibiotics; they are proteins shaped like "Y" that bind to specific antigens, which are recognized as foreign by the immune system.

• Different classes of antibodies exist, such as IgE, which protects against parasitic worms and is involved in allergic reactions. Each antibody is highly specific to its corresponding antigen.

• When antibodies bind to an antigen, they can neutralize pathogens by hindering their movement or reproduction. This binding also signals macrophages to engulf the pathogen.

Activation and Memory Cells in Immune Response

• Both humoral (B cell-mediated) and cell-mediated responses involve memory cells: B memory cells and T memory cells that retain information about previously encountered antigens.

• Memory B cells can activate plasma cells for antibody production, while memory T cells can trigger cytotoxic T cells to target infected cells.

• Vaccines introduce inactive or weakened pathogens to stimulate an immune response without causing disease, leading to the formation of immune memory for future encounters with the pathogen.

Conclusion on Immune System Complexity

• The immune system's complexity is highlighted, noting extensive literature dedicated to its study. Understanding this system is crucial for recognizing how vaccines work and how immunity develops over time.