Microbiology/ Immunology Flashcards
Prokaryotes that may cause infection
Bacteria, rickettsia, and chlamydia
Infectious diseases of the resp tract are most commonly caused by
Viruses
What infection causes more deaths per year than any other bacterial cause?
M. tuberculosis
The majority of skin and soft tissue infections are caused by
Normal skin flora- staphylococcal and streptococcal species
Prokaryotes
Organisms lacking a nucleus and organelles
Cell walls
Generally present in prokaryotes and may be present in eukaryotes. Cell walls protect the microorganism, thus enhancing its survival as well as determining the shape of the micoorganism.
Viruses
Extremely small microbes that are essentially fragments of nucleic acid packaged in a protein shell
Viruses are not living organisms
Their viral nucleic acid is either DNA or RNA, but not both.
Sole activity is replication which can only take place in living cells.
Bacilli
Bacteria rods, may be single or form long chains
Cocci
Bacteria spheres, may exist in pairs (diplococci), chains (streptococci), or clusters (staphylococc i)
Spirochettes
Curved/spiral bacteria
Flagella
Tail like feature that bacteria may possess for motion
Pili
Hair-like structure on bacteria for attachment to host cell surfaces
Plasmids
Small circular molecules of DNA that can replicate independent of the chromosomal DNA. Plasmids have implications relative to conveying resistanceto other bacterial strains through the transfer of genetic information.
Spores
Some bacteria may produce spores that are highly resistant to environmental changes
Notable spore producing bacteria are Clostridium and Bacillus species
Capsule
May surround bacteria and make it less susceptible to destruction by host organism defenses
Mycoplasmas
The smallest, free-living microbes
They lack the bilayered cytoplasmic membrane found in other bacteria, but do not need a host for replication (distinguishes them from viruses)
Do not have cell wall but are bounded by a limiting lipid membrane
Resistant to acid-staining techniques
Obligate intracellular parasites
Unlike other prokaryotes, rickettsiae ad chlamydia require hosts for
metabolic and reproductive activities
Growth curve of bacteria
4 phase
Lag phase- bacteria adapt to their new environment
Logarithmic phase- bacteria double during each reproductive period involving chromosomal duplication and binary fission. Period where symptoms begin to appear. The host is most susceptible to abx at this stage
Stationary phase- reproduction and death rates stabilize.
Decline phase- exponential decline in bacterial numbers
Viral replication cycle
Attachment and penetration followed by biosynthesis, maturation, and release
Lysogeny
When a virus integrates into the host cells DNA rendering them immune to normal host cell defenses.
May establish a latent or dormant stage of the virus within cells that can later reactivate the virus
Fungi groups
Yeast and molds
Hyphae
Long chains of intertwined filaments of fungi.
What distinguishes fungi from bacteria?
Fungi possesses a rigid cell wall and are very large
Opportunistic pathogens
Fungi and other organisms that are normally not pathogenic that cause infectious disease in immunocompromised patients
Fungi reproduction
Both sexual and asexual
Fungi are aerobic organisms except the facultative yeast which can grow in both aerobic and anaerobic environments
Protozoa
Single spore eukaryores that belong in the animal kingdome
Lack cell walls, ingest food particles, and move about ffreely.
Most are harmless, except Plasmodium and Giardia
Metazoans
Helminths (flukes, flatworms, tapeworms) are multicellular organisms with well developed organ structures. Cannot multiple in their hosts and require reexposure for spread of disease.
Most important nonspecific barrier
Skin
Lysozyme
Nonspecific destructive enzyme found in human saliva and tears
Complement proteins
More than 30 proteins circulating in the blood and involved in both nonspecific and specific host immunity.
On invasion, complement may bind to microbial proteins through a process referred to as phagocytosis. Interferons are another form of nonspecific immunity because they trigger the immune system and inhibit viral reproduction.
NK cells function to destroy foreign cells while sparing host cells
Inflammation
Nonspecific immune system
Blood vessels dilate therefore increasing capillary permeability. This action is followed by plasma flow and migration of leukocytes (white blood cells) into the tissue and fluid accumulation
Cytokines are also integrally involved in the inflammatory response, including fever development
Fever
Controlled by the hypothalamus, defined as a body temp above 37.5 C
Proinflammatory cytokines
Interleukins (IL-1, IL-6), TNF-alpha
Leukocytes
Neutrophils (60%)
Monocytes (5%)
Contain enzymes that digest foreign materials after engulfing the invader
Macrophages
Mature monocytes
May initiate the inflammatory response, release cytokines and neutrophil recruitment
Also function as phagocytes in the lymphatic system.
Antigens
Chemicals that trigger specific immunity
What are the foundational cell line to specific immunity?
Lymphocytes (30% of leukocytes)
B vs T lymphocytes
B lymphocytes are largest responsible for antibody mediated immunity
T lymphocytes are largely responsible for cell mediated immunity.
Immunoglobulin
=antibody
Opsonization
Enhancement of phagocytosis by antibodies or complement
T-lymphocytes
Originate in the thymus and populate lymph nodes, the spleen, the tonsils, and other lymphoid tissues
AMI is used in both viral and bacterial host defense while CMI is essential to
viral host defense
Vaccines
Stimulate antibody production as well as T-lymphocytes within the immune system
Acute phase response
Incubation period, prodromal period, acme period
During this phase selected plasma proteins may be produced in the liver (C-reactive protein, serum amyloid A protein). Elevations in these proteins and globulins may be useful as an indicator of disease and are responsible for increases in the erythrocyte sedimentation rate lab test
Bacterial causes of URI
Streptococcus pyogenes and group A streptococcus
Strep throat is caused by
Streptococcus pyogenes
Epiglottitis is caused by
Haemophilus influenzae
Otitis media is caused by
S. pneumonia
Pneumonia
Inflammation of the bronchial tubes and lungs
CAP bacteria
Often pneumococcus, staph aureus
Atypical CAP
Mycoplasma, pneumonia, legionella, pneumophila
Athletes foot is caused by
trichophyton species
Common organisms related to bladder infections
Proteus mirabilis and E. coli
Syphilis
Caused by treponema pallidum
Primary- painless ulcers/chancres on external genitalia and mouth
Secondary- involves many bodily organs spread through the lymph system and circulating blood
Tertiary syphilis- can slowly produce an inflammatory reaction in virtually any organ
Primary target of HIV in humans
CD4 cells (helper T cells)
Categories of immune cells
Lymphoid (B-lymphocytes, T-lymphocytes, NK cells)
Myeloid- monocytes, macrophages, eosinophils, neutrophils, basophils
Innate immunity refers to
the primitive immune response driven by monocytes, macrophages, and neutrophils which recognize pathogens through cell surface interactions and phagocytize them.
Antibody chains
Antibodies can produce one of 5 different classes of heavy chains (alpha, gamma, delta, epsilon, mu)
and either kappa or lambda light chains. Two identical light and heavy chains comprise a single antibody molecule
B-lymphocytes produce _________ as a primary antibody (humoral) response
IgM and then can produce any one of the 5 classes of antibodies in subsequent humoral responses depending on the types of cytokine molecules detected by the B-lymphocyte
Epitopes
A discrete portion of the antigen that antibodies recognize and bind to
Antibody-epitope binding leads to
B-lymphocyte activation involving internalization, processing, and subsequent presentation of antigen with MHC surface molecules as well as production of cytokines, cytokine receptors, and secreted antibodies.
B-lymphocytes present antigens in the context of MHC surface receptors to
T-lymphocytes which then become activated
In addition to antigen recognition, antibodies also
have an effector function in which they bind fragment crystallizable (Fc) receptors on the surface of monocytes, macrophages, neutrophils, mast cells, and T-lymphocytes. These receptors are bound by the Fc region of the antibody, comprised of the constant and class-specific region of the heavy chains
4 types of hypersensitivity
type I (immediate hypersensitivity or allergy) type II (cytotoxic or antibody-dependent [tissue antigen] hypersensitivity) type III (antibody-dependent [soluble antigen] hyper-sensitivity) type IV (delayed-type hypersensitivity).
Myeloid cells
myeloid cells are either antigen-presenting cells (APCs), such as monocytes and macrophages, or granulocytes, such as eosinophils, neutrophils, and basophils.
Function of memory B-cells
Antibody production, antigen presentation
Function of plasma cells
Antibody production
Function of cytotoxic T cells
killing of infected cells
Function of helper t cells
B cell activation
Function of Suppressor T cells
reduction of B and T cells immune responses
Function of NK cells
Killing of tumor cells and virus infected cells
Function of eosinophils
Granule-mediated killing of extracellular pathogens (parasites)
Function of monocytes and macrophages
Antigen presentation, phagocytosis
Function of neutrophils
Phagocytosis, granule-mediated killing
Function of mast cells
Inflammation, allergy
Function of basophils
Inflammation, allergy
Function of platelets
Blood clotting, inflammation
Primary lymphoid organs
Bone marrow and thymus
Produce naive B and T lymphocytes and NK cells
Hematopoietic stem cells
Differentiate into B cells or NK cells. In the bone marrow
Differentiate into T cells in the thymus
Secondary lymphoid organs and tissues
Spleen, lymph nodes, and mucosa associate lymphoid tissues such as tonsils and Peyer’s patches.
What happens when a naive lymphocyte enters the secondary lymphoid tissue?
It recognizes a specific antigen presented by APC such as a macrophage. The antigen-MHC complex is bound by an antigen receptor on the lymphocyte (TCR or BCR). The engagement of the antigen-MHC complex and the antigen receptor causes a cascade of events involving production and secretion of cytokines and chemokines
This process, called clonal selection is necessary for lymphocyte maturation
Do plasma cells proliferate?
No, their function is to produce large amounts of antibodies
MHC molecule
MHC class I- found on the cell surface on most cells in the body. Present intracellular antigens (antigens from pathogens that live and reproduce inside the host cell) MHC class II- found on the cell surface of APCs and present phagocytosed or internalized antigens from external pathogens
When is the t lymphocyte activated?
When the TCR-MHC interaction takes place
T helper cells express _____ cell surface markers
CD4 in conjunction with the TCR and recognize antigens in the context of MHC class II molecules on APCs
Cytotoxic T cells express______
CD8 cell surface molecules in conjunction with the TCR and recognize MHC class I molecules on infected cells
Antibody structure
The antibody is composed of 4 chains linked together by covalent bonds: 2 heavy and 2 light chains
The variable regions (VL and VH) of the light and heavy chains form an antigen-binding site. Therefore, each antibody has 2 antibody binding sites.
Cleavage of an antibody molecule with the cysteine protease papain yields
2 antigen-binding (fab) fragments consisting of one light chain, the VH and CH1 of one heavy vhain, and one fragment crystallizable
Fab fragments functions
to bind antigen because they contain an intact antigen-binding site.
Fc fragment functions
As an effector portion of the antibody
IgA
can be found in the serum, but most often this class of antibody is found as a dimer in mucosal secretions such as saliva, colostrum, milk, tracheobronchial secretions, and urogenital secretions. In its dimerized form, it is referred to as secretory IgA (sIgA).
IgG
the predominant class of antibody found in serum, with four subclasses of IgG molecules. IgG collectively is the major antibody class of secondary (memory) humoral responses. It plays a major role in imparting passive immunity to newborns for the first few months of life because maternal IgG passes across the placenta to the fetus.
IgD
constitutes a small portion of immunoglobulin found in the serum; however, it is usually found in large quantities on the membrane of B-lymphocytes. The precise function of IgD is unknown, but it may play a role in antigen-triggered lymphocyte differentiation.
IgE
least represented antibody class found in the serum. Like IgD, it is overwhelmingly membrane associated, although IgE is found on the surface of mast cells and basophils. Some evidence indicates that this class of antibody participates in immune responses to helminthic parasites; however, in developed countries, it is most associated with allergy-related diseases such as asthma and hay fever.
IgM
is found as a pentamer in serum and as a monomer on the cell membrane of B-lymphocytes. It is found on the surface of naive B-lymphocytes and is the antibody class produced in a primary humoral response.
Groups of cytokines
Interleukins, TNFs, IFNs, growth factors, chemokines, and colony-stimulating factors
