Parasite-Host Interactions and Immune Responses in Parasitology

What factors influence the effect of parasites on their hosts?

Species of the parasite, parasite density, physical condition of the host, nutritional status, and immune status.

What is parenchymatous degeneration?

Swollen cells packed with albuminous or fatty granules, often seen in infected liver, cardiac muscle, and kidney cells.

What does fatty degeneration refer to?

Deposition of abnormal amounts of fat in cells, imparting a yellowish color, commonly seen in parasite-laden liver cells.

What is necrosis in the context of parasite infection?

Degeneration that causes the death of cells or tissues, such as the necrosis caused by encystment of Trichinella spiralis larvae.

What is hyperplasia?

Elevation of the metabolic rate of cells causing cell proliferation, often seen in inflammation.

How does the liver fluke Fasciola hepatica affect bile ducts?

It stimulates excessive division of epithelial cells lining the bile duct, resulting in thickening of the duct wall.

What is hypertrophy?

An increase in cell or organ size due to engorgement by intracellular parasites.

What is metaplasia?

Conversion of one type of tissue into another without embryonic tissue intervention.

What is neoplasia?

Abnormal cell growth that may produce a tumor, which can be benign or malignant.

What is immunity?

The body's ability to prevent the invasion of pathogens by recognizing and protecting against non-self.

What is an antigen?

Any substance that can be recognized by the immune system.

What is an epitope?

The part of the antigen that is recognized by the immune system (antigenic determinant).

What characterizes innate immunity?

It is the first line of defense, fast but nonspecific, using germ-line-encoded recognition molecules and phagocytic cells.

What is adaptive (acquired) immunity?

It involves humoral and cell-mediated responses using B and T lymphocytes, respectively, and is slower to develop.

How do innate and adaptive immunity work together?

Activation of innate immune responses produces signal molecules (cytokines) that stimulate and direct adaptive immune responses.

What are hematopoietic stem cells (HSCs)?

Cells that have the ability to differentiate into many types of blood cells during hematopoiesis.

Where does hematopoiesis occur in adult vertebrates?

In the bone marrow.

What are common myeloid progenitor cells?

Progenitor cells that develop into granulocytes, monocytes, megakaryocytes, and red blood cells.

What is the role of neutrophils?

They are dominant first responders that phagocytose bacteria and secrete proteins with anti-microbial effects.

What is the main role of eosinophils?

Defense against multicellular parasitic organisms, including worms.

What do basophils do?

They release histamine and cytokines that recruit other immune cells.

What are mast cells important for?

They play a key role in the development of allergies.

What do monocytes differentiate into?

Macrophages and dendritic cells, which function in pathogen destruction and antigen presentation.

What are B lymphocytes responsible for?

Producing antibodies and recognizing non-self antigens.

What is the function of T lymphocytes?

They recognize non-self antigens and produce cytokines to activate other immune cells.

What are innate lymphoid cells (ILCs)?

Cells that develop from common lymphoid progenitors and play roles in immune responses.

What is the role of plasma cells?

To produce large amounts of specific antibodies and then die.

What are memory B cells?

Long-lived cells that produce specific antibodies rapidly upon second exposure to an antigen.

What are the three main types of cells that develop from the common lymphoid progenitor?

B lymphocytes, T lymphocytes, and Innate Lymphoid Cells (ILCs)

What is the function of T-helper cells (TH)?

TH cells assist in immune responses; TH1 is active in cell-mediated immunity, and TH2 is active in humoral immunity.

What coreceptor proteins do T-helper cells (TH) have?

CD4 and CD28

What is the role of cytotoxic T lymphocytes?

They bind with target cells and secrete proteins that cause lysis of the target cell's membrane.

What are T-memory cells?

Long-lived cells that are activated during a second exposure to an antigen.

What do Innate Lymphoid Cells (ILCs) include?

Cytotoxic natural killer (NK) cells and non-cytotoxic ILC populations (ILC1s, ILC2s, and ILC3s).

What is the primary function of phagocytosis?

Engulfment and internalization of materials such as microbes for their clearance and destruction.

What are pathogen-associated molecular patterns (PAMPs)?

Conserved patterns found on microbes that are recognized by innate immune system receptors.

What are damage-associated molecular patterns (DAMPs)?

Aging, dead, or damaged self-structures recognized by the immune system.

What is the role of pattern recognition receptors (PRRs)?

They recognize PAMPs and DAMPs and target them for clearance.

What triggers inflammation in the immune response?

Proinflammatory cytokines and chemokines triggered by innate responses to infection, damage, or harmful substances.

What is the major function of adaptive immunity?

To destroy invading pathogens and any toxic molecules they produce.

What is the major histocompatibility complex (MHC)?

A group of genes that code for proteins embedded in cell surfaces, important for self/non-self recognition.

What are the two classes of MHC molecules?

Class I presents intracellular antigens, and Class II presents extracellular antigens.

What is the function of B cells in the humoral immune response?

B cells are activated to secrete antibodies that bind specifically to foreign antigens.

What are the components of an antibody?

Each antibody consists of four polypeptides: two heavy chains and two light chains, forming a 'Y' shaped molecule.

What is opsonization?

The process by which antibodies mark invading pathogens for destruction.

What is the role of cytolytic T lymphocytes (CTLs)?

They lyse cells that display target antigens on their surfaces.

What is delayed type hypersensitivity (DTH)?

A purely cell-mediated response initiated by T cells that requires a delay for the reaction to develop.

What is immediate hypersensitivity (IH)?

A response involving mast cells and IgE antibodies that can lead to allergic reactions and anaphylaxis.

What is the role of dendritic cells in the immune system?

They bridge the innate and adaptive immune systems by presenting antigens to T cells in lymph nodes.

What is the difference between susceptibility and resistance in hosts?

Susceptibility means the host cannot eliminate the parasite, while resistance means the host's physiological status prevents establishment and survival of the parasite.

What is premunition?

A state where the presence of a parasite induces an immune response that restrains its reproduction while the parasite remains alive.

What is concomitant immunity?

A state where the presence of a parasite induces an immune response that conveys resistance to further infection, while the parasite remains unaffected.