Disease & Pathology in Animal Health: Immune and Lymphatic Defenses

Immune System

The coordinated set of cells, tissues, and chemical signals that protects an animal from pathogens and harmful internal changes.

Pathogens

Disease-causing organisms such as viruses, bacteria, fungi, and parasites.

Innate Immunity

Immediate, broad defenses you’re born with, responding quickly to common features of microbes and tissue damage.

Adaptive Immunity

Slower but highly specific immune response that involves memory and provides long-term protection after recovery.

Self vs Non-Self

The immune system's ability to distinguish between its own normal tissues (self) and foreign invaders (non-self).

Tolerance

The immune system's ability to not attack the body’s own tissues or harmless exposures.

Autoimmune Disease

A condition where the immune system mistakenly attacks the body’s own tissues.

Inflammation

A protective response to infection or tissue injury characterized by redness, heat, swelling, pain, and loss of function.

Phagocytosis

The process by which cells, like neutrophils and macrophages, engulf and digest foreign particles.

Complement System

A set of blood proteins that enhances the immune system’s ability to eliminate pathogens.

Natural Killer (NK) Cells

Cells that control infections by targeting and killing host cells that appear abnormal.

Lymphatic System

A network of vessels and organs that returns excess tissue fluid to the bloodstream and supports immune responses.

Lymph

Fluid that originates as plasma and contains water, proteins, dissolved solutes, and immune cells.

Lymph Nodes

Secondary lymphoid organs that filter lymph and serve as activation hubs for immune responses.

Spleen

The organ that filters blood and responds to blood-borne pathogens.

Mucosa-associated Lymphoid Tissue (MALT)

Lymphoid tissues associated with mucosal surfaces that provide local immune responses.

Antigen

A molecule recognized by the adaptive immune system, typically a protein or polysaccharide.

B Cells

Lymphocytes that produce antibodies as part of the humoral immune response.

T Cells

Lymphocytes that play key roles in cell-mediated immunity and require antigen presentation.

Antigen Presentation

The process by which antigen-presenting cells display antigens to T cells.

Clonal Selection

The process by which lymphocytes that recognize an antigen are activated and proliferate.

Humoral Immunity

The aspect of immune response that involves B cells and the production of antibodies.

Cell-mediated Immunity

The aspect of immune response primarily involving T cells that kill infected or abnormal cells.

Lymphatic Obstruction

A condition where lymph flow is blocked, leading to edema and swelling.

Edema

Swelling resulting from the accumulation of excess fluid in tissues.

Immunodeficiency

A weakened immune system that leads to increased susceptibility to infections.

Hypersensitivity

An inappropriate immune response to harmless antigens, leading to allergic reactions.

Chronic Inflammation

Ongoing immune activity that can cause tissue damage and impair function.

Reactive Lymphadenopathy

Enlarged lymph nodes due to immune activation from infection or inflammation.