Natural and artificial immunity

1. Atifa Ambreen
M. Phil, Microbiology
Government College University, Faisalabad

5. Natural Immunity
Naturally acquired active immunity occurs when the person is
exposed to a live pathogen, develops the disease, and becomes
immune as a result of the primary immune response. Once
a microbe penetrates the body's skin, mucous membranes, or
other primary defenses, it interacts with the immune system. B-
cells in the body produce antibodies that help to fight against the
invading microbes. The adaptive immune response generated
against the pathogen takes days or weeks to develop but may be
long lasting, or even lifelong. Wild infection, for example with
hepatitis A virus (HAV) and subsequent recovery, gives rise to a
natural active immune response usually leading to lifelong
protection.

6. Antigen-Antibody Binding
Specificity
An antibody (Ab), also known as an immunoglobulin (lg), is a large, Y-
shaped protein produced mainly by plasma cells that is used by the
immune system to neutralize pathogens such as pathogenic bacteria
and viruses. The antibody recognizes a unique molecule of the
pathogen, called an antigen, via the fragment antigen-binding (Fab)
variable region. Each tip of the "Y" of an antibody contains a
paratope (analogous to a lock) that is specific for one particular
epitope (similarly, analogous to a key) on an antigen, allowing these
two structures to bind together with precision. Depending on the
antigen, the binding may impede the biological process causing
the disease or may activate macrophages to destroy the foreign
substance.

8. Humoral Immunity
Humoral immunity is called active when
the organism generates its antibodies,
and passive when antibodies are
transferred between individuals or species.
Similarly, cell mediated immunity is active
when the organisms' T-cells are stimulated,
and passive when T cells come from
another organism.