The most common form of passive immunity is that which
an infant receives from its mother. Antibodies are transported
across the placenta during the last 1–2 months of
pregnancy. As a result, a full-term infant will have the same
antibodies as its mother. These antibodies will protect the
infant from certain diseases for up to a year. Protection is
better against some diseases (e.g., measles, rubella, tetanus)
than others (e.g., polio, pertussis).
Many types of blood products contain antibody. Some
products (e.g., washed or reconstituted red blood cells)
contain a relatively small amount of antibody, and some
(e.g., intravenous immune globulin and plasma products)
contain a large amount.
In addition to blood products used for transfusion (e.g.,
whole blood, red cells, and platelets) there are three major
sources of antibody used in human medicine. These are
homologous pooled human antibody, homologous human
hyperimmune globulin, and heterologous hyperimmune
serum.
Homologous pooled human antibody is also known as
immune globulin. It is produced by combining (pooling)
the IgG antibody fraction from thousands of adult donors
in the United States. Because it comes from many different
donors, it contains antibody to many different antigens. It is
used primarily for postexposure prophylaxis for hepatitis A
and measles and treatment of certain congenital immunoglobulin
deficiencies.
Homologous human hyperimmune globulins are antibody
products that contain high titers of specific antibody. These
products are made from the donated plasma of humans
with high levels of the antibody of interest. However,
since hyperimmune globulins are from humans, they also
contain other antibodies in lesser quantities. Hyperimmune
globulins are used for postexposure prophylaxis for several
diseases, including hepatitis B, rabies, tetanus, and varicella.
Heterologous hyperimmune serum is also known as antitoxin.
This product is produced in animals, usually horses
(equine), and contains antibodies against only one antigen.
In the United States, antitoxin is available for treatment of
botulism and diphtheria. A problem with this product is
serum sickness, an immune reaction to the horse protein.