1. Immunology
오 상택

2. Purpose
This course aims to gain basic concepts of immune response to infectious agents. Elements of immune system and their roles in defense, organization of immune system, and its relevance to health and diseases will be studied.
Evaluation
Exam. (70%): Mid-term Exam. (100 points), Final Exam. (200 points)
Attendance, homework, quiz (30%)
Textbook
The immune system (Third edition) Peter Parham
Language
Lecture: English, Korean
Exam.: English

3. Elements of the Immune System and their Roles in Defense
Peter Parham
The Immune System
Third Edition
Chapter 1
Elements of the Immune System and their Roles in Defense
Copyright © Garland Science 2009

5. Numerous commensal microorganisms inhabit healthy human bodies
More than 500 microbial species live in the healthy human
 Commensal species
 Micoflora
Commensal organism enhances human nutrition (digestion and providing vitamins) and protect against disease by preventing colonization of pathogens.
 E. Coli secrete antibacterial protein (colicins).
Antibiotics treatments disrupt the natural ecology of the colon.
 Sometimes, it causes further disease.

7. Pathogens are infectious organisms that cause disease
(virus, bacteria, fungi, parasites)

11. The skin and mucosal surfaces form barriers against infection

13. The innate immune response causes inflammation at sites of infection
Innate: they are all determined by the inherited genes.
It consists of two parts: recognition and destructive effector mechanism.
Recognition involves soluble protein (e.g. complements) and cell surface receptor.
Effector mechanisms are provided by effector cells that engulf bacteria, kill virus-infected cells, or attack parasite.

14. The innate immune mechanisms establish a state of inflammation at sites of infection

15. The adaptive immune response adds to an ongoing innate immune response
Recognition mechanism in adaptive immune response is much different from innate immune response whereas effector mechanism is similar.

16. Selection of lymphocytes by a pathogen is occurred during the adaptive immune response

17. Immunological memory in an adaptive immune response
Immunological memory: some of lymphocyte selected during an adaptive immune response persist in the body.
These memory cells allow subsequent encounters with the same pathogen to elicit a stronger and faster adaptive immune response.
Primary immune response
Secondary immune response
 Vaccination

18. Immune system cells with different functions all derive from hematopoietic stem cells

19. Hematopoiesis: generation of blood cells in bone marrow.
Hematopoietic stem cells
Erythroid lineage: erythrocyte, platelet (from megakaryocyte)
Myeloid lineage:
1) Granulocyte: cytoplasmic granules (substance kill pathogen), irregular shaped nuclei.
- Neutrophil: the most abundant, effector cells of innate immunity, phagocytosis of pathogen, short-lived (forming pus)
- eosinophil: defends against parasites
- basophil: defends against parasites

20. 2) Monocyte, macrophage, dendritic cells, mast cells
- Monocyte: mobile progenitor of macrophage
- Macrophage:
residence in tissue
the first phagocytic cell to sense an invading pathogen
general scavenger cells
long-lived commander that orchestrate the local response to infection
secrete cytokines that recruit neutrophils and other leukocytes

21. - Dendritic cells:
are resident in the body’s tissue.
have many properties in common with macrophage.
their unique function is to act as cellular messengers that are sent to call up
an adaptive immune response (tissue to lymphoid organs)
- Mast cells:
is resident in all connective tissue
the activation and degranulation of mast cells at sites of infection make a
contribution to inflammation.
5. Lymphoid lineage
- Natural killer cells (NK cells)
have a granular cytoplasm
are effector cells of innate immunity
defense against viral infection by killing virus-infected cells
- B cell (B lymphocytes)
immunoglobulin surface receptor for pathogen
each B cell expresses a single type of immunoglobulin surface receptor
clonal selection and expansion
differentiate into plasma cells that produce specific antibodies

22. - T cell (T lymphocyte) :
T cell receptor (TCR) for pathogen
each T cell expresses a single type of TCR.
differentiate into cytotoxic T cells and helper T cells.
cytotoxic T cells: kill virus or bacteria infected cells
helper T cells: secrete cytokines that help other cells of immune system become
fully activated effector cells. For example, helper T cells help activate B cells
to plasma cells

23. Most lymphocytes are present in specialized lymphoid tissues
Major lymphoid organ: bone marrow, thymus, spleen, adenoid, tonsil, appendix, lymph nodes and Peyer’s patchs

24. Primary (central) lymphoid tissue:
- lymphocytes develop and mature. (bone marrow and thymus)
- B and T lymphocytes are originate from lymphoid precursors in bone marrow
- B cell complete their maturation in bone marrow
- T cell maturation is occurred in thymus.
3. Secondary (peripheral) lymphoid tissue:
- the sites where mature lymphocytes become stimulated
- lymph node lie at the junctions of lymphatics
- lymphocyte reciruclation
: mature B and T cells move through body in both blood and lymph
- the secondary organs are dynamic tissues in which lymphocytes are constantly arriving from the blood and departing in the lymph (exception: spleen)

26. Adaptive immunity is initiated in secondary lymphoid tissues

27. Architecture of the lymph node, the site where blood-born lymphocytes respond to lymph-born pathogen
Afferent lymphatic vessel: pathogen or pathogen-laden dendritic cells from the infected tissue arrive at a lymph node
T cell area (inner cortex)
B cell area (outer cortex)
Germinal center: expansion of pathogen specific B cell

30. The spleen provides adaptive immunity to blood infections
Direct infected to blood or fail to remove pathogen in lymph node
The spleen is the lymphoid organ that serves as a filter for the blood.
- remove damaged or senescent red cells
- defends the body against blood-born pathogen
Pathogens in the blood are taken up by splenic macrophages and dendritic cells and then stimulate the B and T cells .
Red pulp: red blood cells are monitored and removed.
White pulp: provide adaptive immunity through similar mechanism of lymph node.
5. In spleen, both pathogen and lymphocytes enter and leave the spleen in the blood

32. Most secondary lymphoid tissue is associated with the gut
Gut associated lymphoid tissue (GALT): tonsil, adenoid, appendix, Peyer’s patches
M cells mediates delivery of pathogen to GALT.
GALT are similar to lymph node in their microanatomy.
In the absence of pathogen, lymphocyte that enter GALT from the blood, leave via efferent lymphatics that connet the draining lymph node.
Activated lymphocytes stay in mucosal system, moving to laminar propria and mucosal epithelium, where they perform their effector function.

33. The immune system can be compromised by inherited immunodeficiencies or by the actions of certain pathogens