Lymphocytes and Immunity Clinical Pathology Ms. Canga

Reading Assignment A&P book: pp. 237 – 246 Lab Pro book: pp. 45, & ◦ (There are some very helpful pictures on these pages as well!)

Lymphocytes… …are the predominant WBC in ___________ and ___________. …are the only WBC with no _________________ capabilities. …can constantly recirculate between ____________ and ____________. …may survive for _________ or even ____________. …cannot be differentiated __________________. …can cause __________________. …are predominantly found in _________ and other tissues. Only ~___% of population are in __________________.

Lymphocytes Normal Ranges: 1,000 – 4,800/ in canines and 1,500 – 7,000/ µL in felines WBC originates from PPSCs in bone marrow Immature lymphocytes are processed in the central ________________ organs: ◦ _______________ ◦ _____________________ ◦ ____________ (gut-associated lymph tissue)

Lymphocytes Mature lymphocytes live in the peripheral lymphoid organs ◦ Lymph nodes ◦ _____________ ◦ Bone marrow ◦ GALT ◦ _____________ Fact: The _______________ is the largest lymphoid organ in the body.

Lymphocytes in Circulation The lymphocytes in circulation can be either : ◦ _____________ lymphocytes  Large lymphocytes are thought to be less mature  Have more _________________ that is sky blue  Gradually develop into small lymphocytes ◦ ______________ lymphocytes  _________________ lymphocytes  Very little sky blue cytoplasm usually on one side  May look like a _____________ with no cytoplasm at all!

Small Lymphocyte

Large Lymphocyte

“Reactive or “Atypical” Lymphocytes …may have ________________ granules in the cytoplasm …may have an abnormally shaped _____________. (It may look like a monocyte’s nucleus) …often have larger percentage of ______________ that is very __________________. …may be normal in some _____________ lymphocytes (granules present) …are often associated with chronic antigenic stimulation (common with Canine ____________________)

Lymphocytes at a Glance

Three Types of Lymphocytes _____ – Lymphocytes _____ Cells

T - Lymphocytes Called T – Cells ◦ Processed in __________ before going to periperal tissues. ◦ In thymus, they are “pre-T cells” called __________________  Multiply rapidly  Leave thymus and travel to specific zones in lymph nodes and spleen  Once they leave the thymus, they are functioning, adult T - cells ◦ T-cells are involved in cellular _____________ and activation of ______-lymphocytes. ◦ Most lymphocytes in circulation are ____ - Lymphocytes

B - Lymphocytes Also called B – Cells ◦ Processed in bone marrow and other lymph tissue referred to as “__________ equivalent” ◦ _______________ producing lymphocytes, that are involved in ___________ immunity. (Antigen- Antibody complex)  We will discuss this in detail later

Bursa of Fabricius

B – Lymphocytes & Humoral Immunity Use a “lock and key” type mechanism to fight foreign invaders. ◦ Each B-lymphocyte is pre-programmed to produce only ______ specific ____________ against one specific ________________. ◦ Cell surface has thousands of ________________ against that specific antigen. ◦ Each antigen has a unique shape on it’s surface called an _______________. ◦ When antigen binds with B-cell, __________ -_______________complex is formed.

Antigen – Antibody Complexes Epitope 1234

B- Lymphocytes & Humoral Immunity Specific B-cells are _____-_______________ to recognize specific antigens. ONLY these B-cells will undergo mitotic, _____________ transformation into ________ cells and begin producing antibodies against invaders. All other B-cells are _______________. Potential for over 100 trillion antibodies produced by the body!

Plasma Cells Can ____________, store and ___________ antibodies known as immunoglobulins. (More on this with immunity) Found in any ___________ of body Most numerous in tissues constantly forming antibodies: spleen, lymph nodes Rare in _______________ blood.

Natural Killer Cells Called NK cells ◦ Neither ___ nor ___ lymphocytes ◦ Do not require _______________ by an antigen ◦ Have the ability to kill some types of __________ cells and cells infected with various ___________. ◦ Must come in ____________ contact with cells in order to destroy them.

Lymphocytosis Physiologic: due to _______________ release. Common in chronic __________________. May be caused by ____________ stimulation. Seen in later stages of resolving ____________. Neoplastic lymphocytosis (___________ and lymphosarcoma) Can be significant enough to cause ________________.

Lymphopenia One of the most ____________CBC abnormalities of sick dogs and cats. Associated with __________. Immunosuppressive therapy. Immunodeficiency syndromes. Acute _________ infections Can be significant enough to cause ____________________, especially in _______________.

The Immune System Function: To protect animal from damage/disease. ◦ Recognize “______” from “_________________” ◦ Destroy “______________” Mechanisms of Destruction 1. ___________________ 2. _________(cell membrane) 3. ___________________ 4. ___________________

2 Types of Immunity _________________ immunity ◦ _______ and _______ lines of defense for the body. _______________immunity ◦ _______ line of defense for the body

Non-Specific Immunity First Line of Defense: ◦ _____________ barriers: _________, mucous membranes, etc…  Provide protection by ____________________ microorganisms from entering body. ◦ ______________barriers: Hcl acid of gastric mucosa  Destroy microorganisms that may be ingested.

Non-Specific Immunity Second Line of Defense ◦ ______________________ Response ◦ ______________________ (neutrophils, MPS) ◦ ________Cells ◦ __________________

Nonspecific Immunity (2 nd line of defense) Inflammation ◦ ____________ damage is caused when microorganisms enter the body. ◦ Damage causes release of _______________ factors from cells  One example of chemotactic factor released is from mast cells. (_______________ of tissue)  What is released by mast cells/Basophils?

Inflammatory Response

Inflammation continued

Nonspecific Immunity: Phagocytosis Usually involves ________________, _______________ and tissue ____________________. __________________ initiates the WBC’s death. Accumulation of dead WBCs around site forms ________.

Nonspecific Immunity: NK Cells …are not __-Lymphocytes or __-Lymphocytes. …do not have to be ___________ by a specific antigen. …can kill some types of __________ and tumor cells. …can kill some cells infected with particular __________. …must come in ___________ contact with cell before destroying it.

Nonspecific Immunity: Interferon …is a _____________ produced by a cell after it has been infected by a virus. That cell then dies. …responds rapidly, entering other cells to inhibit further development and spread of the virus.

Overview of Interferon Production

Nonspecific Immunity: Complement …refers to a group of inactive ______________ in plasma. …are activated by attachment of antibody to antigen. …activated enzymes adhere to complement ______________ sites on antigens. -Each plasma enzyme that attaches, causes the activation of another and another, creating a chain reaction until all attachment sites are full. _______________________ fixation - process by which complement enzymes arrange into doughnut formation on antigen surface, create a hole, allowing sodium and water to enter cell and cause it to swell and burst.

Complement Fixation As each binding site is filled, fragments break off and attach to the membrane causing the perforations that eventually lyse the cell.

Specific Immunity The _______ line of defense Primarily involves lymphocytes (__ and __ cells). Includes _____________ and ___________ Immunity Properties of all specific immune responses: 1. Response will be initiated only ________ the antigen enters the body. 2. Response will be aimed specifically against the _______________ present 3. If the antigen enters the body a second time, there will be a ______________ of the antigen and the immune response will occur more quickly.

Cell-Mediated, Specific Immunity A function of __-cell that attaches to the antigen site. Tissue __________________ MUST have ingested antigen and presented its ____________ on its own membrane. ◦ T-cell attaches and becomes a _____________T-cell. Sensitized T-cell divides many times, _________ itself, and forms either ____________T-cell (Tc), a ____________T-cell (Th), or a ______________T-cell (Ts) _____________________ like lymphotoxin are secreted at the site of infection and quickly kill any cell it attacks.

The 3 T-Cells After sensitization by the macrophage, the lymphocyte can become either a _____________ T-cell, a __________T-cell, or a _______________T-cell. ◦ 1) Cytotoxic T-cells (Tc): Are known as __________ T cells. They attach to antigenic cells and destroy them but are not _________________ themselves.

The 3 T-cells 2) __________ T-cells (Th): Are the most numerous of the T cells. They help the immune response by secreting additional _________________ into surrounding tissue. Cytokines can increase activation of ___-cells, ____ cells, or _____ cells. ___________________ is a cytokine that stimulates activity of all other T cells ________________________________________: is a cytokine that attracts tissue macrophages to the area via _______________________ and increases the rate of phagocytosis. (This then, presents more epitopes to the Tc cells!)

The 3 T-cells 3) _________________ T cells (Ts): Operate by ______________ feedback ◦ They ___________ helper T-cells and cytotoxic T- cells. ◦ They ______________ B-cells from transforming into plasma cells. ◦ Help to control cell-mediated and humoral immune responses as infection _______________.

Additional info on Cell-Mediated Immunity T-cells leave the lymphoid tissue and _______________ through blood and lymph. B-cells usually stay in _______________ tissue and send out antibodies found in blood. ◦ Because of this, most lymphocytes in peripheral blood are __-cells. ◦ If a blood smear is made and both B and T cells are present, they will appear ______________.

Humoral Immunity Is a function of __-Lymphocytes B-cells, activated by an _____________- ______________ complex (lock and key system), produce ___________ cells that secrete _________________ into the plasma. B-cells and _____________ cells usually stay in lymphoid tissue. _________________________ (antibodies) circulate in bloodstream (in the ____________), destroying antigens instead of adhering to cells’ membranes.

Antibodies: aka - Immunoglobulins _______ types of antibodies (immunoglobulins) have been identified: ◦ IgG, IgM, IgA, IgE and IgD When an antibody attaches to an antigen: ◦ Antigens may be _________________ into harmless substances. ◦ Antigens may be _______________________ and then phagocytized by macrophages. ◦ _______________________ system may be activated Fact: IgG is present in the greatest quantity of all the immunoglobulins

The 5 Immunoglobulins 1) _______ : Is made during the bodies __________ exposure to an antigen. ◦ Is the first immunoglobulin made by _____________. ◦ Production is relatively _________, so illness may result before production of IgG is complete. 2) ________: Is made when the animal has been exposed to an antigen for an _____________ period of time ◦ Is made upon ________ exposure to an antigen. ◦ Production is __________ than IgG, so illness is less likely.

The 5 Immunoglobulins 3) ________: Plays an important role in preventing disease entering through ____________ or GI tract. ◦ Can leave the __________ and enter tissue fluids. 4) ________: Is associated with _____________ responses. 5) ________: Function is ____________ 

Memory Cells Both ___-cells and ___-cells are capable of becoming Memory Cells Not all activated lymphocytes become immediately involved in the immune response. Memory cells wait for a ___________ infection of the same ____________ that triggered their formation. ◦ May ____________ in blood or wait in ________nodes. ◦ Some can live for a few _______; others for several ___________. Second exposure = more ________ & greater degree of response to antigen than the __________ exposure.