Chapter 12 – Lymphatic System: Immunity (Lecture 2)

These flashcards review key concepts from Chapter 12 on the lymphatic system, emphasizing differences between innate and adaptive immunity, mechanisms of defence, cell types involved, and specific immune responses.

What is immunity in biological terms?

A biological process that protects an organism by identifying and killing pathogens and tumour cells; resistance to particular pathogens, their toxins, or metabolic by-products.

How does the immune system distinguish what it should attack?

By recognizing ‘self’ molecules versus ‘non-self’ (foreign) molecules.

Which two broad subdivisions make up immunity?

Non-specific (innate) immunity and Specific (adaptive) immunity.

What is another name for non-specific immunity, and what role does it play?

Innate immunity; it acts as the primary defence mechanism against invading organisms or pathogens.

Give three examples of non-specific defence mechanisms.

Defence at body surfaces, phagocytosis, natural antimicrobial substances, inflammatory response, immunological surveillance, or fever.

How does the skin provide defence at body surfaces?

It acts as a physical barrier to invasion by pathogens.

What mechanisms in the respiratory system trap and remove pathogens?

Mucus traps dust and pathogens; sneezing, coughing, washing away, or chemical destruction remove them, while nasal hairs filter larger particles.

Which two main cell types perform phagocytosis in innate immunity?

Neutrophils and macrophages.

How do macrophages link innate and adaptive immunity?

After ingesting microbes, they present antigens to T-lymphocytes, activating the specific immune response.

Name four natural antimicrobial substances found in the body.

Hydrochloric acid (HCl), lysozyme, salt from perspiration, slightly acidic saliva, complement proteins, or interferons.

What is the primary function of interferons?

They act as messenger proteins that protect nearby cells from viral infection and cancer, serving as a non-specific defence.

State two objectives of the inflammatory response.

Isolate, inactivate, and remove the cause of damage; remove damaged tissue so wound healing can occur.

What cells carry out immunological surveillance and how do they work?

Natural killer (NK) cells detect abnormal cells and kill them by secreting perforins that lyse the cell membrane and chemicals that enhance inflammation.

Which molecule produced during infection raises the body’s temperature set-point, causing fever?

Interleukin (often called an endogenous pyrogen).

Why does retaining iron during fever hinder bacterial growth?

Bacteria and fungi require more iron at higher temperatures, so withholding iron limits their growth.

List three factors that can modify non-specific immune defences.

Age, hormones, drugs and chemicals, malnutrition, fatigue and stress, or genetic determinants.

Name four characteristic features of specific (adaptive) immunity.

Recognition of self vs non-self, antigen specificity, memory for accelerated second response, and the ability to respond to many different materials.

Which cells produce antibodies in specific immunity?

Plasma cells derived from B lymphocytes.

Define an antigen.

A substance, usually a protein, that is foreign to the body and can stimulate an immune response.

What are haptens and how do they trigger immunity?

Small molecules that cannot elicit an immune response alone but do so when combined with larger carrier molecules; lymphocytes may then react to either component.

Where do T lymphocytes mature, and what percentage of circulating lymphocytes do they form?

They mature in the thymus and form about 70–80% of lymphocytes in peripheral blood.

Where do B lymphocytes mature, and what percentage of circulating lymphocytes do they form?

They mature in red bone marrow and form about 20–30% of circulating lymphocytes.

Differentiate cell-mediated and antibody-mediated immunity.

Cell-mediated immunity (CMI) is mediated by T cells and targets infected or abnormal cells directly, whereas antibody-mediated (humoral) immunity involves B cells producing antibodies that target pathogens outside cells.

Why is each matured T-lymphocyte antigen-specific?

Because it is genetically programmed to recognise only one particular antigen.

What role do antigen-presenting cells (APCs) play in CMI?

Macrophages, B cells, and other APCs process antigens and present them to T cells, initiating the cell-mediated response.

What are cytokines and which cells release them during CMI?

Signal proteins released mainly by T cells and some macrophages that enhance cellular responses to antigens.

What is the function of the major histocompatibility complex (MHC) in immunity?

MHC (HLA) molecules on cell membranes help T cells recognize that an antigen is foreign, not self.

How do helper T cells assist B cells?

Upon activation, helper T cells stimulate B cells to produce specific antibodies against the displayed antigen.

Describe the action of cytotoxic T cells.

They secrete perforins that destroy antigen-bearing cells such as virus-infected or cancerous cells.

What is the purpose of memory T cells?

Produced after initial antigen exposure, they remain poised to provide a rapid, strong response upon future exposures to the same antigen.