OVERVIEW (part 3): adaptive immunity & cells of

the immune systemMarilen M. Parungao-Balolong

BIO 151 Lecture 32nd SEM 2010-2011

Reference: Kuby & Roitt and Roitt

WHAT YOU NEED TO KNOW

• Characteristic Attributes of Adaptive Response

• Lymphocytes as KEY players

• Humoral Immunity Versus Cell-Mediated Immunity

• Antigen Recognition

• Clonal Selection

• Integration: Innate & Adaptive Response

• Cells of the Immune System (Innate and Adaptive)

ADAPTIVE IMMUNITY

• capable of recognizing and SELECTIVELY eliminating SPECIFIC foreign microorganisms and molecules

• not the same in all members of species

• reactions to specific antigenic challenges

CHARACTERISTIC ATTRIBUTES

• Antigenic Specificity

• Diversity

• Immunologic Memory

• Self/Non-Self Recognition

ANTIGENIC SPECIFICITY

• permits it to distinguish even SUBTLE differences among antigens

• Example: Antibodies can distinguish between two protein molecules that differ in only a SINGLE amino acid

DIVERSITY• Diverse RECOGNITION molecules

• allows recognition of billions of unique structures of foreign antigens

IMMUNOLOGIC MEMORY

• exhibited once the immune system has recognized and responded to an antigen

• THUS, the second encounter induces a HEIGHTENED state of immune reactivity

• can confer life-long immunity against many infectious agents after an initial encounter (BASIS for vaccination)

SELF/NON-SELF RECOGNITION

• respond ONLY to foreign antigens

• THUS, an inappropriate response can be fatal...

THE LYMPHOCYTES• An effective immune response involves two major groups of cells: T

lymphocytes and antigen-presenting cells

• Lymphocytes are one of many types of white blood cells produced in the bone marrow by the process of hematopoiesis (TO BE DISCUSSED LATER)

• Lymphocytes leave the bone marrow, circulate in the blood and lymphatic systems, and reside in various lymphoid organs

• Because they produce and display antigen-binding cell-surface receptors, lymphocytes mediate the defining immunologic attributes of specificity, diversity, memory,and self/non-self recognition

• The two major populations of lymphocytes—B lymphocytes (B cells)and T lymphocytes (T cells)—TO BE DISCUSSED IN DETAIL

B-CELLS & T-CELLS

HUMORAL & CELL-MEDIATED IMMUNITY

• HUMORAL: immunity that can be conferred upon a non-immune individual by administration of serum antibodies from an immune individual

• CELL-MEDIATED: can be transferred only by administration of T-cells from an immune individual

ANTIGEN RECOGNITION

PROCESSING AND PRESENTATION

CLONAL SELECTION

INTEGRATION: INNATE & ADAPTIVE

RESPONSE

• Adaptive immune system produces signals and components that stimulate and increase the effectiveness of innate response

• Major difference: rapidity of the innate immune response,which utilizes a pre-existing but limited repertoire of responding components

• Adaptive immunity compensates for its slower onset by its ability to recognize a much wider repertoire of foreign substances,and also by its ability to improve during a response,whereas innate immunity remains constant

• Secondary adaptive responses are considerably faster than primary responses

• Overlapping roles: two systems together form a highly effective barrier to infection

INTEGRATION

Although the innate mechanisms do not improve with repeated exposure to infection as do the acquired, they play a vital role since they are intimately linked to the acquired systems by two different pathways which all but encapsulate the whole of immunology. Antibody, complement and polymorphs give protection against most extracellular organisms, while T-cells, soluble cytokines, macrophages and NK cells deal with intracellular infections

NICE TO KNOW•While an adaptive immune system is found only in

vertebrates, innate immunity has been demonstrated in organisms as different as insects,earthworms,and higher plants

•Dysfunctions of the immune system include common maladies such as allergy or asthma

•Loss of immune function leaves the host susceptible to infection;

•in autoimmunity,the immune system attacks host cells or tissues

CELLS OF THE IMMUNE SYSTEM•Hematopoiesis

•Stem Cells

•Apoptosis or Programmed Cell Death: induced and ordered process in which the cell actively participates in bringing about its own demise = a critical factor in the homeostatic regulation

APOPTOSIS

CELLS INVOLVED IN INNATE IMMUNITY

a-b: monocytec: neutrophils and

eosinophild-e: neutrophilsf: inflammatory

cellsg-h: macrophages

i: basophilj-k: mast cells

CELLS INVOLVED

IN ADAPTIVE IMMUNITY

a: lymphocytesb: T-cellsc: B-cells

d-e: plasma cellsf: Langerhan’s cells (leprosy)

next meeting: ANTIGENS &

IMMUNOGENS