Medical Immunology: Lymphoid System Overview

Which organ is classified as a primary lymphoid organ?

What primarily mediates the earliest phases of inflammatory reactions?

Which of the following is NOT a secondary lymphoid organ?

What is one function of macrophages?

What do class I and II MHC receptors on macrophages primarily function as?

Which cytokines are primarily associated with the development of lymphoid cells?

What type of cell arises from myeloid lineage in the bone marrow and circulates in the blood?

Which of the following statements about mononuclear phagocytes is true?

What is the primary function of antigen-presenting cells (APCs)?

Which of the following cytokines is produced by macrophages as part of the innate immune response?

Which type of immune response do dendritic cells primarily participate in?

Which of the following cells are primarily responsible for the direct presentation of antigens to helper T cells?

What is the role of mast cells in the immune response?

Which cytokine is NOT typically associated with macrophage function?

What is the classification of phagocytosis in the context of immune responses?

Which of the following correctly identifies a function that is innate and a function that is acquired?

The Lymphoid System

Composed of primary and secondary lymphoid organs.
Primary lymphoid organs:
- Bone marrow
- Thymus
Secondary lymphoid organs:
- Lymph nodes
- Spleen
- Tonsils
- Mucosa-Associated Lymphoid Tissues (MALT) of the GIT and respiratory tract

Pluripotent Stem Cells

Located in the bone marrow
Differentiate into lymphoid or myeloid series
Influenced by soluble mediators like IL-7, IL-3, and colony stimulating factors

Cells of the Immune System

Phagocytes

Neutrophils:
- Also known as polymorphonuclear leukocytes.
- Most abundant circulating white blood cells.
- Important for early inflammatory responses.
Mononuclear Phagocytes:
- Monocytes: Circulate in the blood and mature into macrophages in tissues.
- Tissue resident macrophages: Found in various tissues and originate from precursors in the yolk sac and fetal liver.
Macrophage Functions:
- Phagocytosis (innate)
- Antigen processing and presentation (acquired)
- Cytokine production (innate and acquired)
- Complement synthesis (innate)
Mast Cells, Basophils, and Eosinophils:
- Mast cells are found in skin and mucosal epithelia and contain histamine-filled granules.
- Basophils and eosinophils are granulocytes with distinct functions in immune responses.

Antigen-Presenting Cells (APCs)

Capture antigens and present them to lymphocytes.
Dendritic cells:
- Most important APCs for activating naive T cells.
- Link innate and adaptive immune responses.
Macrophages:
- Present antigens to helper T cells and stimulate macrophage activation.
B cells:
- Present antigens to helper T cells, important for antibody responses.

Main Antigen-Presenting Cell

Dendritic cells are the primary antigen-presenting cells.

Explore the components and functions of the lymphoid system in this quiz. You will learn about primary and secondary lymphoid organs, pluripotent stem cells, and the various cells involved in the immune response, including phagocytes. Test your knowledge on key immune system concepts.