Lecture 5 Flashcards
(36 cards)
What is the difference between innate and adaptive immunity?
Innate immunity: Receptors recognize conserved structures present in many pathogens (Pathogen-associated Molecular Patterns): LPS, peptidoglycan, lipids, mannose, bacterial DNA and viral RNA
Adaptive immunity: Receptors recognize a specific structure unique to that pathogen, and has “memory”
What are the features of adaptive immune responses?
specificity, diversity, memory, clonal expansion, specialization, contraction and homeostasis, and non-reactivity to self
What are lymphocytes?
Mediators of adaptive immune responses; only cells with specific receptors for antigens (e.g., T-cells, B-cells)
What are Antigen-presenting cells APC, and what is its role?
Specialized to capture, concentrate, and display antigens for recognition by lymphocytes
ex: Dendritic cells; macrophages, B-cells; follicular dendritic cells
What are effector cells, and what is its role?
Function to eliminate microbes; includes lymphocytes, granulocytes (neutrophils, eosinophils), macrophages
What are the 2 arms of adaptive immune response?
Humoral: antibodies (proteins produced by B-cells) that circulate in the blood. Antibodies can recognize the infected cells and free microbes (bacteria and viruses).
Cellular: Lymphocytes (T-cells) that do not produce a soluble product. T-cells can recognize the infected cells, but not free microbes.
Describe the lymphocyte antigen receptor of B and T-cells.
The B-cell antigen receptor is a membrane-bound antibody - SURFACE IMMUNOGLOBULIN.
The T-cell antigen receptor IS NOT membrane bound antibody but a distinct molecule - T-CELL ANTIGEN RECEPTOR
Each antigen receptor binds to a different antigen and Each cell has only one antigen specificity
What is the structure of T-cell receptors?
T-Cell Receptors for Antigens Consist of 1 Alpha Chain and Beta Chain Linked by a Disulfide Bridge
What are MHC molecules?
Are encoded by a family of genes called the major histocompatibility complex to which t-cells bind
infected cells produce MHC molecules that binds to antigen fragments and then are transported to the cell surface in a process called antigen presentation
What are the 2 different classes of MCH (HLA) molecules?
MHC Class I – Universal, located in the ER membrane
MHC Class II – Specialized cells (macrophages, dendritic cells, B-cells), located in the cytoplasm
What is the difference between MHC class 1 and 2?
MHC-1 has longer alpha chain that is membrane bound, but does not have a beta that is membrane bound
both classes process and bind to peptide
What are central lymphoid organs?
THYMUS – T cell maturation
BONE MARROW – B cell maturation
What are peripheral lymphoid organs?
LYMPH NODES
SPLEEN WHITE PULP
MUCOSA-ASSOCIATED LYMPHOID TISSUE
Describe progenitor cells in the thymus.
P-cell progenitor undergoes maturation and gives rise to different t-cells with different receptors on it. The body has to decide which are useful among them…it undergoes positive and negative selection. Less than 1% is selected and the rest is nuclear apoptosis (about 3-4 days) Positive – test all t-cells for ability to bind MCH class molecules with an antigen bound to it…if it can't bind at all, it gets eliminated You want to have a binding that is low to intermediate. If you have binding that is too tight then the negative selection comes into play --> too strong of binding, then the t-cells can become active against our own bodies Negative – if the binding is really strong of t-cells to MCH class molecules
What is lymphocyte amplification AKA Adaptive immunity?
Adaptive immunity has capacity to increase its number of the functional/effector cells to keep up with the number of microbes In the body to eliminate the pathogen
describe lymphatic release of antibodies.
Lymphocytes can release antibodies that can bind directly to circulating pathogen and can lead to the neutralization to the microbe, preventing it from interacting with the host cell.
Antibodies can also activate the complement system or decorate the surface of the antigen so that can be detected by macrophages and be gobbled up and destroyed
Describe differentiation of lymphocytes.
Once you go through differentiations and have specialized T-cells, you can have H(helper) t-cells.
Helper cells have the macrophage antigen, and the t-cells to it, and it releases cytokines to activate macrophages to help fight off the infection. It can also signal other t-cells and b-cells.
Cytotoxic lymphocytes - Engage the effector cells by engaging the surface molecule presented in the antigen. The CTL directly kills the effector cell in this case.
Both are examples of cellular base immunity
What is the role of T-helper cells, cytotoxic t-lymphocytes, and plasma cells?
t-helper- activates b-cells and macrophages, and releases cytokines
cytotoxic t-lymphocytes - kill virus-infected cells
plasma cells - produce antibodies
What is the difference of activation of TH2 and TH1?
TH2 – get activated by B-cells,
and TH1 - by macrophages
Describe TH1 and TH2 cell activity.
TH1 – Macrophages and antigen-presenting cells. We have bacteria and the Micro comes in and starts chopping up microbe into pieces, and it loads them into MHC class 2 molecules (has this in addition to class 1) which get transported to the surface of the cell. MCH1 gets recognized by t-helper type 1 that releases signaling molecules that can act on infected cell, get it activate and help it get rid of the antigen. The same is happening in the surface of a B-cell for TH2
Why are antibodies limited in function?
Antibodies limited in function because of their location…they aren’t good at clearing up intercellular pathogens cus they can’t get to them
What is the purpose of clonic selection of B-cells?
Clonal selection of B cells generates a clone of short-lived activated effector cells and a clone of long-lived memory cells
What is the job of dimer cells?
to produce antibodies (along with the plasma cells)
What is the purpose of antibodies sticking around after fighting off infection?
Some antibodies stick around and serve as memory cells so the next time the antigen comes in, you will get a more rapid response
Antibodies have specific receptors that it can only recognize antigens for the receptor