INTRODUCTION & OVERVIEW OF IMMUNOBIOLOGY

BIOLOGY 151 LECTURE 1

Marilen M. Parungao-Balolong

Associate Professor

IMMUNOLOGY/ IMMUNOBIOLOGY

• Immunology = study of our protection from foreign macromolecules or invading organisms and  our responses to them

• INVADERS = viruses, bacteria, protozoa or even larger parasites

• immune responses DEVELOPED against our own proteins (and other molecules) in autoimmunity and against our own aberrant cells in tumor immunity

OVERVIEW OF THE

IMMUNE SYSTEM

• composed of two major subdivisions, the innate or non-specific immune system and the adaptive or specific immune system

• each of the major subdivisions of the immune system has both cellular and humoral components by which they carry out their protective function

• these two arms of the immune system have distinct functions, there is interplay between these systems (i.e., components of the innate immune system influence the adaptive immune system and vice versa)

FIRST LINE OF DEFENSE = innate or non-specific

• barrier tissues such as the skin that stop the entry of organism into our bodies

• IF these barrier layers are penetrated, the body contains cells that respond rapidly to the presence of the invader

• EXAMPLE = macrophages and neutrophils that engulf foreign organisms and kill them without the need for antibodies

• EXAMPLE = soluble molecules that deprive the invading organism of essential nutrients (such as iron) and from certain molecules that are found on the surfaces of epithelia, in secretions (such as tears and saliva) and in the blood stream

2ND LINE OF DEFENSE = specific or adaptive

• may take days to respond to a primary invasion (that is infection by an organism that has not hitherto been seen)

• production of antibodies (soluble proteins that bind to foreign antigens) and cell-mediated responses in which specific cells recognize foreign pathogens and destroy them

• EXAMPLE = response in recognition and destruction of virally-infected or tumorigenic cells

• response to a second round of infection is often more rapid than to the primary infection because of the activation of memory B and T cells

• signals may be proteins such as lymphokines, cytokines and chemokines which stimulate cells of the immune system 

CELLS OF THE

IMMUNE SYSTEM

• All cells of the immune system have their origin in the bone marrow which differentiate along distinct pathways (to discuss later)

• The myeloid progenitor (stem) cell in the bone marrow gives rise to erythrocytes, platelets, neutrophils, monocytes/macrophages and dendritic cells whereas the lymphoid progenitor (stem) cell gives rise to the NK, T cells and B cells

• For T cell development the precursor T cells must migrate to the thymus where they undergo differentiation into two distinct types of T cells, the CD4+ T helper cell and the CD8+ pre-cytotoxic T cell

• Two types of T helper cells are produced in the thymus the TH1 cells, which help the CD8+ pre-cytotoxic cells to differentiate into cytotoxic T cells, and TH2 cells, which help B cells, differentiate into plasma cells, which secrete antibodies

FUNCTION OF THE IMMUNE SYSTEM

• The main function of the immune system is self/non-self discrimination

• ability to distinguish between self and non-self is necessary to protect the organism from invading pathogens and to eliminate modified or altered cells (e.g. malignant cells)

FUNCTION OF THE IMMUNE SYSTEM

• NOTE: when the virulence of the invading organism is great or when immunity is compromised = DISEASE

• detrimental effects = inflammation, which is the response to an invading organism, there may be local discomfort and collateral damage to healthy tissue as a result of the toxic products produced by the immune response

• the immune response can be directed toward self tissues resulting in autoimmune disease

International Journal of Infectious DiseasesVolume 3, Issue 1, July-September 1998, Pages 54-60

▪ 2001 – Discovery of FOXP3 – the gene directing regulatory T cell development ▪ 2005 – Development of human papillomavirus vaccine (Ian Frazer)

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IMMUNITY