• Antibodies (Immunoglobulins)
    • Main component of the humoral response of the adaptive immune system
    • Y-shaped proteins
    • Recognize and bind antigens
      • Binding to antigens attracts innate immune cells to phagocytose and destroy the pathogen
    • Produced by B cells
      • Each B cell makes a single type of antibody or immunoglobulin, which can recognize and bind to a specific antigen 
      • Can exist as membrane-bound cell receptors or independently in circulation 
    • Structure of an antibody
      • Two identical heavy chains and light chains
        • Connected by disulfide bonds
      • Both heavy and light chain involved in forming:
        • Constant region
          • Does not bind antigens
          • Signals to other cells (eg, phagocytes) and proteins to destroy antigen bound at other end
        • Variable region
          • Binds antigen
          • Unique amino acid structure of this region determines specificity of antibody