Overview of the Immune System

The body's first line of defense against pathogens, it's non-specific and includes physical barriers, cellular responses, and the complement system.

External defenses like skin, mucus membranes, and hairs that prevent pathogens from entering the body.

White blood cells that engulf and destroy pathogens.

A response that brings white blood cells to an infected area to fight infection and limit its spread.

A group of proteins that work together to destroy pathogens by puncturing their membranes.

A non-specific immune response present from birth, providing initial defense against infection.

A specific immune response developed over time, targeted to a specific invader.

A response that occurs without prior exposure to a specific antigen.

A response that stems from prior exposure to a particular antigen.

The ability of the adaptive immune system to remember previous infections, leading to a faster and stronger response upon re-exposure.

A type of white blood cell crucial for adaptive immunity, including B and T cells.

An immune response involving T cells, where cells directly attack infected or abnormal cells.

An immune response mediated by antibodies produced by B lymphocytes.

Unique proteins found on the surface of cells that act like identification tags, allowing the immune system to distinguish between different cell types.

The process of coating a pathogen with proteins (opsonins) that makes it easier for phagocytes (white blood cells) to engulf and destroy it.

Complement activation leads to: 1. Opsonization (making pathogens easier to eat), 2. Inflammation (bringing more immune cells to the site), and 3. Cell lysis (killing pathogens directly).

The complement system can form a 'membrane attack complex' (MAC) that creates holes in the membrane of pathogens, leading to their death.

The immune system is comprised of cells, tissues/organs, and effector molecules. Cells are the basic building blocks that carry out specific functions, tissues/organs provide structure and support, and effector molecules are the chemical signals and weapons used in the immune response.

White blood cells, also known as leukocytes, are crucial for immune defense. They include various types like lymphocytes (T cells and B cells), neutrophils, macrophages, and others, each playing specific roles in recognizing and neutralizing threats.

The immune system relies on tissues and organs for proper functioning. Skin, the body's largest organ, provides a physical barrier. Bone marrow produces many immune cells. The thymus matures T cells. Lymph nodes filter lymph fluid and provide a site for immune cell interactions. The spleen removes old cells and stores immune cells. Mucosal-associated lymphoid tissue (MALT) and Gut-associated lymphoid tissue (GALT) are found in mucosal linings and protect against infections.

Effector molecules are the chemicals that the immune system uses to communicate, identify threats, and neutralize them. The complement system proteins create holes in pathogens' membranes. Cytokines are signaling molecules that coordinate immune responses. Antibodies bind to pathogens and signal for their destruction. There are other effector molecules with various roles.

Antigens are substances that trigger an immune response, essentially anything the immune system recognizes as foreign. These can be microbial proteins or carbohydrates, parts of neoplastic cells, or even environmental factors like pollen or animal dander.

Cytokines are small proteins, like messengers, that facilitate communication between immune cells. They coordinate responses, amplify immune reactivity, and can be categorized into families like colony-stimulating factors (CSF), interferons (IFN), interleukins (IL), and lymphokines.

Chemokines are a special type of cytokine that attract immune cells called leukocytes to sites of inflammation. They are vital for coordinating immune responses and directing the movement of white blood cells to areas needing immune support.

CD stands for 'Cluster of Differentiation'. These are surface molecules found on immune cells that can be used to identify different types of cells based on the specific molecules they express. For example, CD4+ T cells are a type of T cell that have the CD4 marker on their surface.