Host Resistance & Immunity

Innate (nonspecific)

Host defenses that include first line of defense & second line of defense

• body’s natural, inborn defense system provides protection against wide range of foreign invaders

Acquired (specific)

Host defenses, third line of defense

• immunity develops over time in response to exposure

first line of defense

surface protection composed of anatomical & physiological barriers that keep microbes from penetrating sterile body compartments

• Ex: physical barriers, chemical barriers, genetic components

second line of defense

cellular & chemical system that comes immediately into play if infectious agents make it past surface defenses

• Ex: phagocytosis, inflammation, fever, antimicrobial proteins

third line of defense

includes specific host defenses that must be developed uniquely for each microbe through the action of specialized white blood cells

• include active infection & passive maternal antibodies

• B cells, T cells, & their effects

hematopoesis

development of white blood cells in bone marrow

macrophages & dendritic cells

What are the innate leukocytes?

basophils

release histamine which causes inflammation

• nuclei with two to five lobes

eosinophils

defend against protozoan & helminths parasites

• nuclei with two to five lobes

neutrophils

highly phagocytic & kill ingested microbes with lytic enzymes

• nuclei with two to five lobes

B & T cells

WBCs that aren’t yet activated after leaving bone marrow become part of the adaptive immune response

Megakaryocyte

Hematopoietic stem cell > Common Myeloid Progenitor > Megakaryoblast > _____ > platelets

• platelets involved in blood clotting & inflammation

mast cells

specialized tissue cells similar to basophils that trigger local inflammatory reactions & are responsible for many allergic symptoms

• Hematopoietic stem cell > common myeloid progenitor > putative mast cell precursor > ___ ___

Granulocytes

Include eosinophils, basophils, & neutrophils

• Hematopoietic stem cell > common myeloid progenitor > myeloblast

monocyte

blood phagocytes that rapidly leave the circulation; mature into macrophages & dendritic cells: common myeloid progenitor > monoblast > ____

• macrophages - largest phagocyte ingest & kill foreign cells; strategic participants in certain specific immune reactions

• dendritic cell - reside throughout tissue, processing foreign matter & presenting it to lymphocytes

Agranulocytes

No granules in cytoplasm includes:

• monocytes, T cells, & B cells

T cells

perform number of specific cellular immune responses, assist B cells & kills foreign cells (cell-mediated immunity)

• Hematopoietic stem cell > common lymphoid progenitor > lymphoblasts

B cells

differentiate into plasma cells & form antibodies (humoral immunity)

• Hematopoietic stem cell > common lymphoid progenitor > lymphoblasts

Skin

Strong mechanical barrier, keratin

Inhospitable environment

• shedding skin

• pH acidic

• high NaCl concentration

• subject to periodic drying

mucous membranes

Form protective covering that resists penetration & traps microbes in various antimicrobial substances

• Lysozyme - hydrolyzes bond connecting sugars in peptidoglycan

• eye: mucous, flushing of tears, lysozyme, & secretory IgA in tears

lysozyme

hydrolyzes bond connecting sugars in peptidoglycan

Mucociliary blanket

Mucous secretions traps microbes, these microbes are transported from the lungs via mucociliary escalatory

• expelled by coughing/ sneezing

• salivation washes microbes to stomach

alveolar macrophages

phagocytic cells in alveoli of lungs

IgA & defensins

In the gastrointestinal tract, plasma cells secrete what two products:

Paneth cells

Cells found in the gastrointestinal tract that produces lysozyme & cryptins

low, lactobacilli, urea

Genitourinary tract unfavorable environment:

• ____ pH of urine & vagina

• vagina has _______

• _____ & other toxic metabolic end products in urine

Cationic peptides

Antimicrobial peptides divided into three classes, has the ability to damage bacterial cell membranes

first class

Cationic peptide: linear, alpha-helical peptides that lack cysteine amino acid residues

• Ex: cathelicidin, produced by a variety of cells

cathelicidin

A first class cationic peptide produced by a variety of cells

second class

Defensins

• cationic peptide

• found inn neutrophils, intestinal Paneth cells, respiratory epithelial cells

third class

Cationic peptide: larger peptides

• Ex: histatin, present in human saliva & has anti-fungal activity

Histatin

A third class cationic peptide:

• present in human saliva & has anti-fungal activity

Opsonization

Process in which microbes are coated by serum components (opsonin) in preparation for recognition/ ingestion by phagocytic cells

• some complement proteins are opsonins

complement activation

Proteins working in cascade pathways to eliminate pathogen

• must be activated in cascade fashion

• 3 pathways: alternative, lectin, classical

cytokines

soluble proteins or glycoproteins released by one cell population that act as intercellular mediators or signaling molecules

• 3 groups based on function:

  • regulators in innate resistance mechanisms

  • regulators of adaptive immunity

  • stimulators of hematopoiesis

monokines

cytokines that are released from mononuclear phagocytes

lymphokines

cytokines released from T lymphocytes

interleukins

cytokins released from one leukocyte & act on another leukocyte

Colony stimulating factors (CSFs)

stimulate growth & differentiation of immature leukocytes in bone marrow

• type of cytokine

Antibodies

Immunoglobulins, glycoprotein made by activated B cells (plasma cells)

• serves as antigen receptor on B cell surface

• Classes: IgG1, IgM, IgA2, IgD, IgE

IgM

first Ig in all immune responses

• agglutination, activates complement

• expressed as membrane-bound antibody on B cells

IgA

an Ig: secreted across mucosal surfaces

• Tears, saliva, breast milk

IgG

involved in opsonization, neutralization of toxins

• only Ig that can cross placenta

IgD

Ig that’s part of the B cell receptor complex

• signals B cells to start antibody production

precipitation, opsonization, neutralization, complement fixation, agglutination

What are consequences of antigen-antibody binding? (5)

precipitation

Consequence of antigen antibody binding: cell-free molecule in solution

neutralization

Consequence of antigen antibody binding: antibodies block binding

complement fixation

Consequence of antigen antibody binding: lysing bacterial cells

agglutination

Consequence of antigen antibody binding: cross linked bacterial cell antigen

antigen

Recognized as foreign & invoke immune response (B cell activation > production of antibodies)

• name comes from antibody generators

• self & nonself that elicit immune response

• large, complex molecules

antigenic determinant sites (epitopes)

site on antigen that reacts w/t specific antibody or T cell receptor

• valence is number of epitopes on an antigen

Identification of self & foreign, diversity, specificity, memory

What are characteristics & types of specific immunity? (4)

humoral immunity

antibody mediate immunity

• based on antibody activity

cellular immunity

cell-mediated immunity

• based on action of specific kinds of T lymphocytes

Acquired immunity

a type of immunity that develops over time as a result of exposure to pathogens or vaccines

• divided into natural vs artificial, both are further subdivided into active & passive

natural immunity

Acquired immunity through normal life experiences & not induced by medical means

• active: conseq of person developing own immune response to microbe (infection)

• passive: one person receiving preformed immunity made by another (maternal antibody)

artificial immunity

acquired immunity via medical procedures (immunization)

• active: consequence of person developing their immune response (vaccination)

• passive: consequence of one receiving performed immunity made by another (immune globulin therapy)