Download Haemophilus influenzae

Introdução ao sistema e à resposta imune
• Um pouco de história
•Vacinas e outras imunizações
Tabela 1-1. Eficiência da vacinação no controle de doenças infecciosas comuns
Doença
Max. number of
cases
Number of cases in
2003
Percent
change
Diphtheria
206,939 (1921)
1
-99.99
Sarampo
894,134 (1941)
42
-99.99
Caxumba
152,209 (1968)
194
-99.90
Coqueluche
265,269 (1934)
8,483
-96.80
Polio (paralytic)
21,269 (1952)
0
-100.0
Rubella
57,686 (1969)
8
-99.97
Tetanus
1,560 (1923)
14
-99.10
Haemophilus
influenzae type B
∼20,000 (1984)
20
-99.90
Hepatitis B
26,611 (1985)
6,711
-75.03
Tabela 1-2. Características da resposta inata e da adaptativa
Innate
Adaptive
Characteristics
Specificity
For structures shared by groups For antigens of microbes and for
of related microbes
nonmicrobial antigens
Diversity
Limited; germline-encoded
Very large; receptors are produced by
somatic recombination of gene segments
Memory
None
Yes
Nonreactivity to
self
Yes
Yes
Physical and
chemical
barriers
Skin, mucosal epithelia;
antimicrobial chemicals
Lymphocytes in epithelia; antibodies
secreted at epithelial surfaces
Blood proteins
Complement
Antibodies
Cells
Phagocytes (macrophages,
neutrophils), natural killer cells
Lymphocytes
Components
Table 1-3. Cardinal Features of Adaptive Immune Responses
Feature
Functional significance
Specificity
Ensures that distinct antigens elicit specific responses
Diversity
Enables immune system to respond to a large variety of antigens
Memory
Leads to enhanced responses to repeated exposures to the same
antigens
Specialization
Generates responses that are optimal for defense against different
types of microbes
Self-limitation
Allows immune system to respond to newly encountered antigens
Nonreactivity
to self
Prevents injury to the host during responses to foreign antigens
Evolução do sistema imune
Innate immunity
Adaptive immunity
Phagocytes
NK cells
Antibodies
T & B lymphocytes
Lymph nodes
Protozoa
+
-
-
-
-
Sponges
+
-
-
-
-
Annelids
+
+
-
-
-
Arthropods
+
-
-
-
-
Elasmobranchs (sharks,
skates, rays)
+
+
+ (IgM
only)
+
-
Teleosts (common fish)
+
+
+ (IgM,
others?)
+
-
Amphibians
+
+
+ (2 or 3
classes)
+
-
Reptiles
+
+
+ (3
classes)
+
-
Birds
+
+
+ (3
classes)
+
+ (some
species)
Mammals
+
+
+ (7 or 8
classes)
+
+
Invertebrates
Vertebrates
Protective immunity against microbes is mediated by the early reactions of innate immunity and the
later responses of adaptive immunity. Innate immunity is stimulated by structures shared by groups
of microbes. Adaptive immunity is specific for different microbial and nonmicrobial antigens and is
increased by repeated exposures to antigen (immunologic memory).
Humoral immunity is mediated by B lymphocytes and their secreted products, antibodies, and
functions in defense against extracellular microbes. Cell-mediated immunity is mediated by T
lymphocytes and their products, such as cytokines, and is important for defense against
intracellular microbes.
Immunity may be acquired by a response to antigen (active immunity) or conferred by transfer of
anti-bodies or cells from an immunized individual (passive immunity).
The immune system possesses several properties that are of fundamental importance for its
normal functions. These include specificity for different antigens, a diverse repertoire capable of
recognizing a wide variety of antigens, memory for antigen exposure, specialized responses to
different microbes, self-limitation, and the ability to discriminate between foreign antigens and self
antigens.
Lymphocytes are the only cells capable of specifically recognizing antigens and are thus the principal
cells of adaptive immunity. The two major subpopulations of lymphocytes are B cells and T cells, and
they differ in their antigen receptors and functions. Specialized antigen-presenting cells capture
microbial antigens and display these antigens for recognition by lymphocytes. The elimination of
antigens often requires the participation of various effector cells.
The adaptive immune response is initiated by the recognition of foreign antigens by specific
lymphocytes. Lymphocytes respond by proliferating and by differentiating into effector cells, whose
function is to eliminate the antigen, and into memory cells, which show enhanced responses on
subsequent encounters with the antigen. The activation of lymphocytes requires antigen and
additional signals that may be provided by microbes or by innate immune responses to microbes.
The effector phase of adaptive immunity requires the participation of various defense
mechanisms, including the complement system and phagocytes, that also operate in innate
immunity. These mechanisms neutralize and eliminate the microbes and antigens that elicited the
response.