Biology 151 (introduction to Immunology) Lecture 1

1. INTRODUCTION & OVERVIEW OF
IMMUNOBIOLOGY
BIOLOGY 151
LECTURE 1
Marilen M. Parungao-
Balolong
Associate Professor

2. 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

3. 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)

4. 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

5. 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

6. 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

7. • 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

8. 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)

9. 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

10. International Journal of Infectious Diseases
Volume 3, Issue 1, July-September 1998, Pages 54-60

17. ▪
2001 – Discovery of FOXP3 – the gene directing regulatory T cell development
▪
2005 – Development of human papillomavirus vaccine (Ian Frazer)

19. NEXT MEETING:
INNATE & ADAPTIVE
IMMUNITY