General Pathology Lecture 9: Immunity

What are the two functions of innate immunity?

1. Protect against pathogens

2. Clear damaged cells

What do phagocytes, dendritic cells, and epithelial cells all contain to detect pathogens?

Cell receptors

Which cell receptor subtype recognize microbial molecules?

Toll-like receptors

Which cell receptor subtype recognize compounds released from damaged cells?

NOD-like receptors

Which cell receptor subtype activates capase-1 that activates IL-1?

Inflammasome

Which cell receptor subtype recognize fungal glycans?

C-type lectin receptors

What are the two effects of inflammation?

1. Promote release of cytokines

2. Recruit WBCs

What is released for antiviral defense?

Interferons

What is the pathologic response to variety of previous antigenic (foreign) substances?

Adaptive immunity

What three things is adaptive immunity a response to?

1. Pathogens

2. Chemicals

3. Transplanted tissues

What are the two types of adaptive immunity?

1. Humoral

2. Cellular

What cell acts in humoral adaptive immunity?

B lymphocytes

What is the function of B lymphocytes?

Produce antibodies that attack extracellular pathogens

What are the three sites of B lymphocytes?

1. Blood

2. Mucosal surfaces

3. Tissues

What cell acts in cellular adaptive immunity?

T lymphocytes

What are the two functions of T lymphocytes?

1. Attack intracellular pathogens

2. Help B lymphocytes produce antibodies

What do T lymphocytes release to activate phagocytes?

Cytokines

What is the indirect form of immunologic protection from pathogens/infectious diseases?

Herd immunity

What probability is lowered through herd immunity?

Infection to others without acquired immunity

What causes herd immunity?

Vaccination

What is the percentage of population that needs to be vaccinated for herd immunity?

60 - 80%

What is the percentage of population that needs to be vaccinated for herd immunity with COVID-19?

80 - 90%

What are the two types of lymphoid tissue?

1. Generative

2. Peripheral

What is the function of generative lymphoid organs?

Lymphocyte progenitor stem cell development

What is the site of generative lymphoid organ development (T & B lymphocytes)?

Bone marrow

What is the site of generative lymphoid organ maturation (T lymphocytes)?

Thymus

What is the function of peripheral lymphoid organs?

Concentrate antigens and lymphocytes

What are the three sites of peripheral lymphoid organs?

1. Lymph nodes

2. Spleen

3. Skin/mucosa

What is the main oral lymphoid tissue?

Tonsils

What are the two accessory oral lymphoid tissues?

1. Tonsillar arch

2. Ventral tongue/floor of the mouth

What do T lymphocytes contain to distinguish lymphocytes?

Surface receptors

What do lymphocytes only bind to?

Peptide fragments

What do MHC peptides recognize?

Foreign proteins

What does CD4 bind to on antigen-presenting cells?

Class II MHC

What is the site of CD4?

Epithelial cells

What does CD8 bind to on antigen-presenting cells?

Class I MHC

What are the three sites of CD8?

1. Nucleated cells

2. Platelets

3. Transplanted tissue

What is MHC also known as?

Human Leukocyte Antigen complex

MHC peptides are generated by a gene on which chromosome?

Chromosome 6

What allows organ donation between identical twins without rejection?

Similar MHCs

What is the main function of cytokines to enhance immunity?

Cell-cell chemical messengers

Which cells are helper T lymphocytes?

CD4

What are the two functions of CD4?

1. Trigger B cells to produce antibodies

2. Recruit macrophages

What is the normal range of CD4 cells?

500—1,500 μL T cells

What is the amount of CD4 cells that indicate HIV?

< 200 μL

Which cells are cytotoxic T lymphocytes?

CD8

What is the amount of CD8 cells that indicate HIV?

> 1,200 μL

What is the function of CD8 cells?

Directly kill virally-infected cells

What is the function of TH1 CD4 Helper cells?

Provide host defense for intracellular pathogens

What is the target for TH1 CD4 Helper cells?

Macrophages

What is the function of TH2 CD4 Helper cells?

Stimulate B cells to differentiate into eosinophils

What response does TH2 CD4 Helper cells act in?

Allergic reactions

What is the function of TH17 CD4 Helper cells?

Provide host defense for extracellular pathogens

What is the target for TH17 CD4 Helper cells?

Neutrophils

What do stimulated B cells differentiate into in bone marrow?

Plasma cells

What do B lymphocytes release antibodies into?

Blood/lymph fluid

In what two organs are NK cells produced in?

1. Thymus

2. Bone marrow

Do NK cells require prior sensitization?

No

What two things do NK cells kill?

1. Infected cells

2. Cells beyond repair

Do NK cells damage healthy cells?

No

What are the three types of antigen presenting cells?

1. Dendritic

2. Macrophages

3. B cells

What is the most important antigen presenting cell?

Dendritic cells

What are the antigen presenting cells in the epithelium?

Langerhans cells

What is the function of dendritic cells?

Capture antigens and present to CD4

What are naïve T lymphocytes activated by?

Antigen exposure

What do naïve T lymphocytes differentiate into?

Effector cells

What do effector cells that remain become?

Memory cells