FUNCTIONS OF

T LYMPHOCYTES

BY:

Roll

NO:102,108,114,120

,126

Presented by:1. Memoona Zamurad (102)2. Maryam Ikram (108)3. Mavra Hafeez (114)4. Mommal Rasool (120)5. Noreen Riaz (126)

INTRODUCTION

Main defense systems of body Skin Glands and their secretions White blood cells : Lymphocytes

B Lymphocyt

es

T Lymphocyt

es

Anti body production

Self activation

ORIGIN AND PROCESSING:

Originate in Bone marrow Pluripotent hematopoetic stem cells

common lymphoid progenitor cells Proliferation and education in THYMUS

gland. Reaction against self-antigens ;90-95%

cells destroyed. Specificity

TYPES OF T LYMPHOCYTES CD 4-helper T Cells CD 8-cytotoxic T cells Suppressor T Cells Memory cells

HELPER T CELLS Helper T cells; CD4 3/4 of T cells. Types : TH1 and TH2 Major regulators : LYMPHOKINES

PRODUCTION(That act on other cells as well as on bone

marrow) Include;

Interlukin-2,3,4,5,6 , granulocyte-monocyte colony stimulating factor, interferon-&.

AIDS; destruction of helper T cells

FUNCTIONS OF HELPER CELLS; Stimulation of cytotoxic and suppressor

T cells. Stimulation of B-cell growth and

differentiation to form plasma cell clones

Activation of Macrophage system Feedback stimulatory effect on helper T

cells themselves.

DIAGRAM

CYTOTOXIC T CELLS Killer cells ; CD8 Direct attack on micro-organisms PERFORINS : hole-forming proteins Release of cytotoxic substances into the

attacked cells Cell swell and thus destroy. Lethal to TISSUE CELLS invaded by

VIRUSES. Important role in destroying CANCER

CELLS, HEART TRANSPLANT CELLS, or other cells foreign to body.

SUPPRESSOR T CELLS Less known cells Suppress function of cytotoxic and

helper T cells. Prevent damage to body itself REGULATORY CELLS along with helper

cells IMMUNE TOLERANCE:

MEMORY T CELLS These are activated by antigens but do

not enter in circulation Remain in lymphoid organs Migrate to various lymphoid tissues

throughout the body If attacked by same antigen again,

immediate response. More POWERFUL response

DISORDERS RELATED TO T LYMPHOCYTES

Autoimmune disorders

Immune deficiency diseasesAllergic reaction

Tissue rejection

AUTO-IMMUNITY IMMUNE TOLERANCE; unresponsiveness

of immune system to any substance capable to elicit immune response.

Developed in THYMUS ( self-antigen reaction)

BUT IF IT FAILS……. AUTO-IMMUNITY: 2 types

Organ specific Organ non-specific

BYSANDER EFFECT; inflammation sensitizes neighboring T cells which would not respond normally

IMMUNO DEFICIENCY DISEASES “Defective immune system” pathogens

attack easily OPPURTUNISTS; organisms taking

advantage of defective defense mechanism.

2 TYPES: CONGENITAL immunodeficiency

diseases (inherited defect in immune system)

ACQUIRED immunodeficiency diseases ( infection by some pathogen)

T CELLS RELATED CONGENITAL DISORDERS: DIGEORGE’S SYNDOME; absence of

thymus gland genetically SCID-Bubble boy disease; lack of ADA

enzyme due to defect at chromosome 22, lymphoid tissue absent

ACQUIRED DISEASES OF T-CELLS AIDS LYMPHOMA Lymphoma: “solid tumor of

lymphoid cells” may develop in bone marrow , spleen,

lymph nodes, blood or any other organ. Fast and abnormal division of

lymphocytes .

AIDS ( ACQUIRED IMMUNE DEFICIENCY SYNDROME) Cause; HIV Cd4 COUNT ; Less than 200 cells/mm3

while normal is 500-1500cells/mm3. MODE OF ACTION: Glycoprotein from HIV binds to specific

receptor on cd4 cells. release of HIV RNA into host cell action of REVERSE TRANSCRIPTASE viral RNA viral DNA new HIV form, host cell burst and virus

enter in bloodstream, infecting more cells,

SYMPTOMS OF AIDS INCUBATION PERIOD: No symptoms for

several weeks after exposure Symptoms develop when sufficient number

of cells ruptured COMMON symptoms are ; fatigue chronic diarrhea loss of appetite night sweat low-grade fever oral ulcers vaginal ulcers etc

OPPURTUNISTIC INFECTIONS: Which mostly kill the AIDS patient are Pneumocystis pneumonia Kaposi sarcoma ( malignant skin cancer) Respiratory tract infections Lymphomas Mode OF TRANSMISSION: Exposure to secretions from infected person

i.e through blood transfusion,from mother to fetus and by vaginal sexual intercourse

PREVENTION; Awareness among people Blood screening

NORMAL LYMPHOCYTE COUNT AND ABNORMALITIES 15OO-4000cells/ul of blood. 20;40% of total WBCs LYMPHOCYTOSIS: “Increased

lymphocytes” 1) ABSOLUTE L.C increased i.e. total lymphocytes greater than 4000.

2 )RELATIVE L.C increased i.e. increased proportion of lymphocytes than 40% but Absolute count IS NORMAL

LYMPHOCYTOPENIA: “ Decreased lymphocytes than 1000cells/ul.”

ALLERGY-DELAYED RESPONSE Is caused by activated T cells. An inflammatory reaction Secondary response appearing after 48-

72 hours of exposure. Poison ivy rash: serious tissue damage

of skin on repeated exposures. Lungs edema Aesthematic attacks

TRANSPLANT REJECTION T cells cause tissue rejection of any

foreign tissue or organ transplanted. PREVENTION => by killing T cells by Azathioprine. => inhibit cytotoxic T cells proliferation

by Glucocorticoids ( Cushing syndrome ).

=> immunosuppressive drugs such as Cyclosporine.