1. Immune Response Adaptive Immune Response

2. Adaptive Immune 2 Adaptive Immune Response Humoral Immunity B cells Cellular Immunity T cells

3. Adaptive or Acquired Immune Response  Protects against infectious agents and abnormal body cells  Amplifies the inflammatory response  Activates complement 3

4. Adaptive Defenses 4  Adaptive immune response  Is systemic  Is specific  Has memory  Two separate overlapping arms 1. Humoral (antibody-mediated) immunity 2. Cellular (cell-mediated) immunity

5. Acquired or Adaptive Immune Response There are two major branches of the adaptive immune response  Humoral  Antibody- mediated immune response  Mediated by B-lymphocytes  Cellular  Cell-mediated immune response  Involves the production of cytotoxic T- lymphocytes, activated macrophages, activated NK cells, and cytokines in response to an antigen  Mediated by T-lymphocytes 5

6. Antigens  Substances that can mobilize the adaptive defenses and provoke an immune response  Most are large, complex molecules not normally found in the body (nonself)

7. Acquired or Adaptive Immune Response  During adaptive immunity:  Bone marrow & thymus (primary lymphoid tissues) produce B cells and T cells, respectively  Immature T cells migrate to thymus and become competent T cells  B cells and T cells recirculate through spleen and lymph nodes (secondary lymphoid tissues)  Antigen (Ag) presenting cells (APC) pick up antigen and migrate to secondary lymphoid tissues & interact with T cells and B cells 7

8. Antigenic Determinants  Certain parts of an entire antigen that are immunogenic  Antibodies and lymphocyte receptors bind to them

9. Antigenic Determinants  Most naturally occurring antigens have numerous antigenic determinants that  Mobilize several different lymphocyte populations  Form different kinds of antibodies against it  Large, chemically simple molecules (e.g., plastics) have little or no immunogenicity

10. Examples  “Simple” molecules  Stainless steel  plastics

11. Examples 11

12. Cells of the Adaptive Immune System  Two types of lymphocytes  B lymphocytes (B cells)—humoral immunity  T lymphocytes (T cells)—cell-mediated immunity  Antigen-presenting cells (APCs)  Do not respond to specific antigens  Play essential auxiliary roles in immunity

13. Antigen Processing and Presentation  In order to generate adaptive immunity, as well as long lasting memory, Ag should be recognized by T and B cells  Lymphocytes make up to a billion different types of antigen receptors  Memory usually improves upon repeated exposure to a given infection 13

14. Antigen-Presenting Cells (APCs)  Engulf antigens  Present fragments of antigens to be recognized by T cells  Major types  Dendritic cells in connective tissues and epidermis  Macrophages in connective tissues and lymphoid organs  B cells

15. Differences in Innate and Adaptive Immunity  The innate and adaptive immune responses both function to protect against invading organisms, but they differ in a number of ways  (1) The innate immune system is constitutively present and reacts immediately to infection. The adaptive immune response to an invading organism takes some time to develop  (2) The innate immune system is not specific in its response and reacts equally well to a variety of organisms, whereas the adaptive immune system is antigen-specific and reacts only with the organism that induced the response  (3) The adaptive immune system exhibits immunological memory. It "remembers" that it has encountered an invading organism (antigen) and reacts more rapidly on subsequent exposure to the same organism. The innate immune system does not possess a memory. 15

16. Acquired Immunity Type of ImmunityHow acquired by HostExamples Active ImmunityOccurs when an individual is exposed to an infectious agent or one of its products (antigens) Active Natural Immunity: Antibodies are produced by the host in response to the infectious agent itself (e.g. Recovery from disease) Active Artificial Immunity: Occurs through vaccination with a form of the disease microorganism. It may be dead, attenuated (weakened), or altered so that it will not produce the disease but will cause the body to produce antibodies. Passive Immunity As a result of acquisition of antibodies which have been produced by another animal (by active means) or derived from cells grown in tissue culture Passive Natural Immunity: Transfer of antibodies from a mother to her baby through the placenta; Transfer of antibodies from mother to infant in milk if nursing. Passive Artificial Immunity: Acquired through inoculation with antibodies. Injection of immune serum from an individual previously immunized or recovered from disease 16