Chapter 15: The Adaptive Immune Response

General Characteristics of the Adaptive Immune Response Involves specialized WBC’s known as lymphocytes Response is highly specific (molecular specificity) Response generates memory Can discriminate between self and non-self (tolerance)

Overview of the Adaptive Immune Response

Anatomy of the Lymphoid System Lymphatic Vessels form lymph Secondary lymphoid Organs Lymph nodes, spleen, tonsils, peyer’s patches Primary Lymphoid Organs Bone marrow and thymus

Peyer’s Patch is example of secondary lymphoid organ

Lymphocytes are responsible for the adaptive immune response

What promotes an immune response? Antigens Any molecule that reacts with antibody, B cell receptor or T cell receptor Composition is usually proteins or polysaccharides Foreign substance with MW of 10,000 daltons Examples of antigens: bacterial capsules, cell walls, flagella, toxins of bacteria

Antibodies bind antigens

Small molecules are not recognized as antigens until bound to another

How are antigens recognized? Self markers also known as MHC markers MHC (major histocompatibility complex) MHC Class I-produced by all body cells MHC Class II-produced by dendritic cells, B cells, and macrophages These cells are also called antigen presenting cells (APCs)

How are B cells activated?

B cell activation by Helper T cell

Structure of an antibody

There are 5 classes of antibodies IgM IgG IgA IgE IgD

Immunoglobulins

Naïve B cells produce IgM, then IgG antibodies

Primary and secondary response to antigen

What can happen when antibody binds antigen?

T-independent antigens activate B-cells without T cells

Let’s look at the T cells Have own T cell receptor (TCR) Do not make antibodies Must recognize MHC markers which “present” antigen

T cells differ from B cells Must use MHC markers on host cells to recognize antigens

Antigen recognition by T cells occurs with MHC:TCR binding

How are T cells activated?

Effector functions of Cytotoxic T cells

Effector function of Helper-T cells

Effector function of Helper-T cells

Natural Killer Cells…lymphocyte but not a T cell

Antibody dependent cell mediated cytotoxicity