Immune System Study Guide

Being exposed to pathogens indicates something is wrong within the body.
Neutrophils are attracted to sites of injury or infection to fight pathogens.
The rationale behind attracting neutrophils is that they help to eliminate anything causing cell injury.

Refers to the process where neutrophils change shape to squeeze between cells at the site of injury.

Involves the release of chemicals that attract additional immune cells to the site of infection.
Positive Chemotaxis: Immune cells are attracted to the source of signals indicating infection or injury.
Negative Chemotaxis: Cells are repelled by certain signals, although this term is not commonly used in inflammation.

Monocytes typically transform into macrophages around twelve hours after an injury.
Macrophages begin to replace neutrophils as infection progresses, as neutrophils get destroyed.
The goal of inflammation is to clear the area of pathogens, dead cells, and debris to facilitate tissue repair.

Pus primarily consists of neutrophils and dead cells (including endothelial cells) from the site of infection.
Certain pathogens have the ability to resist macrophages and may remain alive, forming granulomas surrounded by macrophages. These granulomas can lead to disease.

Interferons and complement proteins are significant antimicrobial proteins produced during immune responses.
Antimicrobial proteins differ from antibodies, which are part of adaptive immunity.
- Interferons:
- Induced by viral infections; they alert neighboring cells about viral activity.
- Interferons signal uninfected cells to prepare for potential infection by increasing antiviral defenses.
- Effective in activating Natural Killer (NK) cells that destroy infected cells.
- Complement Proteins:
- Circulate in an inactive form; their activation amplifies inflammatory processes.
- They help in the destruction of foreign substances by tagging them for phagocytosis and enhancing inflammation.

Classical Pathway: Involves antibodies that tag pathogens for destruction.
Lectin Pathway: Involves lectins recognizing foreign invaders and activating complement.
Alternative Pathway: Involves spontaneous activation of complement.

All pathways converge on C3, which splits into C3b (promoting opsonization) and C3a (enhancing inflammation).

Fever is a complex body response often triggered by pyrogens, substances that indicate infection or inflammation.
Increases the body's metabolic rate, enhances immune cell migration, and can inhibit bacterial growth by raising body temperature.

Innate immunity is non-specific and acts immediately to identify and remove pathogens without the ability to remember previous encounters.

Involves specific responses and the capability to remember previously encountered pathogens.
Key players in adaptive immunity are T cells and B cells, which have distinct roles:
- B Cells: Responsible for humoral immunity by producing antibodies.
- T Cells: Responsible for cellular immunity, directly killing infected host cells.

Defined as any substance that can evoke an immune response.
- Complete Antigens: Stimulate immune responses and activate lymphocytes.
- Incomplete Antigens (Haptens): Small molecules that only trigger an immune response when attached to a larger protein.

Must be activated by T helper cells before they can produce antibodies.
After activation, they differentiate into plasma cells that secrete antibodies specific to the presented antigens.

Divided into CD4 (Helper T Cells) and CD8 (Cytotoxic T Cells):
- CD4 T Cells: Recognize antigens presented on Class II MHC and activate B cells and other immune cells.
- CD8 T Cells: Recognize antigens on Class I MHC on infected cells and destroy them.

Class I MHC: Present on all nucleated cells, displays self-antigens and signals cytotoxic T cells.
Class II MHC: Present only on antigen-presenting cells (like dendritic cells, macrophages, etc.), activates helper T cells.
Activation requires T cell receptors to recognize both the MHC and the presented antigen.

Memory cells remain after primary immune response enabling a quicker response upon re-exposure to the same antigen.
Vaccines aim to invoke such memory without causing disease, often requiring boosters to maintain immunity due to changing pathogens.

Active Immunity: Acquired through infection or vaccination.
Passive Immunity: Temporary immunity received through placenta or breastfeeding or through medical interventions (e.g., monoclonal antibodies).

Understanding both innate and adaptive immune mechanisms is crucial for studying diseases, vaccines, and therapeutic approaches in immunology.
A good grasp on how various components function together assists in comprehending the overall immune response and potential medical applications in vaccinations and treatments.