Immunology-II (Adaptive Immunity)

Innate/natural defenses

present at birth, provide nonspecific resistance to infection

adaptive immunities

specific, must be acquired

immune system

a large, complex, and diffuse network of cells (WBC) and fluids that penetrate into every organ and tissue

recognition of foreign material vs. self

PAMPS vs. PRRs

Survey the body

Extracellular fluid/RES, blood, lymphatic system

destruction of entities deemed to be foreign

• inflammation

• chemical response

• phagocytosis

memory

once exposed to an antigen, certain immune cells remember the antigen and respond rapidly and vigorously against it

antigen

fragment of protein (left over from pathogen)

• stimulates the adaptive immune system

• free floating or in the host

Major Histocompatibility Complex (MHC)

• present antigens

• all cells have MHC-I (if phagocytic)

• immune cells ahve MHC-II

yes

are neutrophils phagocytic?

yes

are eosinophils phagocytic?

no (releases chemical (ex: histamine))

are basophils phagocytic?

no

are lymphocytes phagocytic

lymphocyte

• responsible for adaptive immune response

• develop into B and T cells

yes

are monocytes phagocytic?

monocyte

develop into macrophages

thymus gland and bone marrow

primary organs of the lymphatic system

thymus gland

generates T-cell lymphocytes

Bone marrow

generates B-cell lymphocytes

circulatory based locations (lymph nodes, spleen, tonsils, Peyer’s Patches)

secondary organs and tissues

lymph nodes

small, encapsulated, bean-shaped organs stationed along lymphatic channels and large blood vessels

B-cell receptors

find free antigens

T-cell receptors

bind processed antigens together with MHC

a single specificity

Each genetically different type of lymphocyte expresses…

alternative splicing

How are the various types of receptors made?

antigen

a substance that provokes an immune response in specific lymphocytes

antigenicity

property of behaving as an antigen

epitope

small, molecular group that is recognized by lymphocytes

• antigenic determinant

• where the receptor recognzies the antigen

immunoglobulins

large glycoproteins that serve as specific receptors of B cells

• can be attached to B-cell or secreted

antibodies

immunoglobulins that are secreted

T-cell receptors

have constant and variable regions that recognize antigens

• not secreted, always stay attached

primary response to antigens

• latent period with no measurable antibody occurs early on

• the first antibody to appear is IgM, followed later by IgG arising from activation of the first memory cells.

• Within weeks, the titer tapers back to low levels

secondary response to antigens

• a latent period is lacking because other memory lymphocytes from the earlier response are immediately ready to react.

• a rapid rise in antibody titer, mainly of IgG, is sustained for several weeks.

• a smaller amount of IgM is also produced by naive B cells.

functions of antibodies

• bacterial cell “tagged” with Abs

• opsonization

• neutralization

• agglutination

• complement fixation

• precipitation

opsonization

phagocytosis by leukocyte after pathogen is targeted by antibody

neutralization

antibodies block binding

agglutination

lock and cross-linked bacterial cells

• can’t move → can’t infect host cell

complement fixation

lysing bacterial cells

precipitation

antibodies aggregate antigen molecules

classic complement system

a series of proteins activated by interactions with antigen-antibody complexes in a sequence that result in:

• Gram (+) → increased opsonization

• lysis of Gram (-) cells by formation of a membrane attack complex

  • poke holes in membrane