Cells of the Immune System (PART I - GRANULOCYTES) (FL-Immuno/02)

Summary

This video lecture introduces the cells of the immune system, specifically granulocytes, which are white blood cells with visible cytoplasmic granules. It explains the classification of granulocytes into basophils, eosinophils, and neutrophils, each with distinct characteristics and functions. Basophils are involved in inflammation and allergic reactions, eosinophils defend against parasites, and neutrophils are active phagocytes that respond quickly to infection. Additionally, mast cells, similar to basophils, play a role in inflammation. The lecture provides a detailed overview of these immune cells, their functions, and their role in the body’s defense mechanisms.

Takeaways

• 😀 The immune system consists of cells, molecules, tissues, and organs, with immune cells known as leucocytes (white blood cells).
• 😀 Leucocytes arise from bone marrow and are found in blood and lymph, spreading throughout the body.
• 😀 Leucocytes are classified into granulocytes and agranulocytes based on the appearance of their cytoplasmic granules under a microscope.
• 😀 Granulocytes have clearly visible granules, while agranulocytes have uniform cytoplasm without visible granules.
• 😀 Granulocytes are further divided into three types: basophils, eosinophils, and neutrophils, each with distinct characteristics.
• 😀 Basophils have heavily granulated cytoplasm and are involved in inflammation and allergic reactions, staining blue-purple with basic dyes.
• 😀 Eosinophils have a two-lobed nucleus and play a role in defending against protozoan and helminthic parasites, staining red or orange with acidic dyes.
• 😀 Neutrophils are the most abundant white blood cells, with a multi-lobed nucleus, and are active phagocytic cells that respond first to infections.
• 😀 Neutrophils contain three types of granules that help in killing and digesting microbes, and they migrate to infection sites in response to signals.
• 😀 Mast cells resemble basophils in appearance and function, playing a role in inflammation and allergic responses, and are found in tissues like skin and connective tissue.

Q & A

What is the immune system, and what are its main components?

The immune system is the collection of cells, molecules, tissues, and organs that work together to defend the body against harmful pathogens. Its main components include white blood cells (leukocytes), antibodies, the lymphatic system, and various organs like the spleen and thymus.

What is the Greek origin of the term 'leukocyte'?

The term 'leukocyte' comes from Greek, where 'leukos' means white, and 'kutos' means cell. Therefore, leukocytes are white blood cells.

Where do leukocytes originate and mature?

Leukocytes originate from the bone marrow, where most of them develop and mature.

What are the two main classifications of leukocytes?

Leukocytes are classified into two main groups: granulocytes and agranulocytes. This classification is based on the appearance of granules in their cytoplasm under a light microscope.

What distinguishes granulocytes from agranulocytes?

Granulocytes have visible granules in their cytoplasm, which can be seen under a microscope, while agranulocytes do not have these visible granules.

What are the three types of granulocytes, and how are they characterized?

The three types of granulocytes are basophils, eosinophils, and neutrophils. They are characterized by the shape of their nuclei and the staining properties of their granules under a microscope.

What role do basophils play in the immune response?

Basophils play a role in inflammation and allergic responses. They contain granules that release vasoactive mediators like histamine, which influence blood vessel tone and diameter.

What distinguishes eosinophils in terms of their function and appearance?

Eosinophils have a two-lobed nucleus and granules that stain red or orange with acidic dyes. They are involved in defending the body against protozoan and helminthic parasites and play a role in allergic reactions.

How do eosinophils attack large parasites like protozoa and helminths?

Eosinophils do not ingest large parasites through phagocytosis. Instead, they attach to the surface of the parasites and release substances that are harmful to and destroy the parasites.

What are neutrophils, and what role do they play in immune defense?

Neutrophils are the most abundant type of leukocyte, with a multi-lobed nucleus. They are active phagocytic cells that migrate to the site of infection, where they ingest and destroy microbes. They also contain antimicrobial substances in their granules.

What is the function of mast cells, and how are they related to basophils?

Mast cells are similar to basophils in both appearance and function. They contain granules with vasoactive mediators and play a role in inflammation and allergic responses. However, mast cells are typically found in tissues like the skin and mucosal surfaces.

How are neutrophils different from other granulocytes in terms of their lifespan and role in immune defense?

Neutrophils are the first cells to migrate to the site of infection, but their lifespan is relatively short, lasting only a few days. They provide an initial defense but are not involved in long-term immune responses, unlike other immune cells.