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One important difference between BCRs and TCRs is the way they can interact with antigenic epitopes. Whereas TCRs can only interact with antigenic epitopes that are presented within the antigen-binding cleft of MHC I or MHC II , BCRs do not require antigen presentation with MHC; they can interact with epitopes on free antigens or with epitopes displayed on the surface of intact pathogens. Another important difference is that TCRs only recognize protein epitopes, whereas BCRs can recognize epitopes associated with different molecular classes (e.g., proteins, polysaccharides, lipopolysaccharides).

Activation of B cells occurs through different mechanisms depending on the molecular class of the antigen. Activation of a B cell by a protein antigen requires the B cell to function as an APC, presenting the protein epitopes with MHC II to helper T cells. Because of their dependence on T cells for activation of B cells , protein antigens are classified as T-dependent antigens . In contrast, polysaccharides, lipopolysaccharides, and other nonprotein antigens are considered T-independent antigens because they can activate B cells without antigen processing and presentation to T cells.

A B cell plasma membrane has two long rectangles spanning it; these form a Y shape. Two shorter rectangles sit on the outside of the upper portion of the Y. The region spanning the membrane and half-way through the bars of the Y is the constant region. The upper region is the variable region which has the antigen binding sites. The long rectangles are the heavy chain. The shorter rectangles are the light chains. Multiple disulfide bridges hold the constant region together.
B-cell receptors are embedded in the membranes of B cells. The variable regions of all of the receptors on a single cell bind the same specific antigen.
  • What types of molecules serve as the BCR?
  • What are the differences between TCRs and BCRs with respect to antigen recognition?
  • Which molecule classes are T-dependent antigens and which are T-independent antigens?

T cell-independent activation of b cells

Activation of B cells without the cooperation of helper T cells is referred to as T cell-independent activation and occurs when BCRs interact with T-independent antigens. T-independent antigens (e.g., polysaccharide capsules, lipopolysaccharide) have repetitive epitope units within their structure, and this repetition allows for the cross-linkage of multiple BCRs, providing the first signal for activation ( [link] ). Because T cells are not involved, the second signal has to come from other sources, such as interactions of toll-like receptors with PAMPs or interactions with factors from the complement system .

Once a B cell is activated, it undergoes clonal proliferation and daughter cells differentiate into plasma cells. Plasma cells are antibody factories that secrete large quantities of antibodies. After differentiation, the surface BCRs disappear and the plasma cell secretes pentameric IgM molecules that have the same antigen specificity as the BCRs ( [link] ).

The T cell-independent response is short-lived and does not result in the production of memory B cells . Thus it will not result in a secondary response to subsequent exposures to T-independent antigens.

A circle with small chains of hexagons projecting from the surface is a pathogenic bacterial cell. The chains are polysaccharide antigens with repeating epitopes. Antibodies on the B cell bind to these epitopes. This causes the activation of the  B cell and secretion of pentameric IgM.
T-independent antigens have repeating epitopes that can induce B cell recognition and activation without involvement from T cells. A second signal, such as interaction of TLRs with PAMPs (not shown), is also required for activation of the B cell. Once activated, the B cell proliferates and differentiates into antibody-secreting plasma cells.

Questions & Answers

Who is the founder of spontaneous generation
Elina Reply
The Theory of Spontaneous Generation. The Greek philosopher Aristotle (384–322 BC) was one of the earliest recorded scholars to articulate the theory of spontaneous generation, the notion that life can arise from nonliving matter.
What is Tecochi Acid
Atreyee Reply
it is the main memory of a person.
Kizza Reply
what is brain
Tope Reply
is the main memory of a person.
it is the centre of the nervous system found in all vertebrates and most invertebrates.
what are the two acids the skin produce
Caro Reply
alpha hydroxy and beta hydroxy there are water soluble compounds and often use as exfoliant
hlo caro
what is pooled sample
what must a positive strand of an RNA virus do first
Kelsi-Ann Reply
A positive-sense single-stranded RNA virus (or (+)ssRNA virus) is a virus that uses positive sense single stranded RNA as its genetic material. Single stranded RNA viruses are classified as positive or negative depending on the sense or polarity of the RNA.
 The positive-sense viral RNA genome can serve as messenger RNA and can be translated into protein in the host cell. Positive-sense ssRNA viruses belong to Group IV in the Baltimore classification. Positive-sense RNA viruses account for a large fraction of known viruses, including many pathogens
such as the hepaci virus C, West nail virus, dengue virus, SARS and MERS coronaviruses, and SARS-CoV-2 as well as less clinically serious pathogens such as the rhinoviruses that cause the common cold.
Why strong acid and alkline are not harmful to mycobacterium bacili?
What are the types of bacteria
John Reply
Do you mean the shapes or the the two different types of bacteria? Bacteria are often described in terms of their general shape. Common shapes include spherical (coccus), rod-shaped (bacillus), or curved (spirillum, spirochete, or vibrio) The two different types are gram negative or gram positive.
what other characteristics of prokaryotes a bacteria don't have?
Prokaryotes are single-celled organisms belonging to the domains Bacteria and Archaea. Prokaryotic cells are much smaller than eukaryotic cells, have no nucelus, and lack organelles. All prokaryotic cells are encased by a cell wall. Many also have a capsule or slime layer made of polysaccharide.
gram positive bacteria and gram negative bacteria
Most bacteria can be broadly classified as Gram positive or Gram negative. Gram positive bacteria have cell walls composed of thick layers of peptidoglycan.cells stain purple when subjected to a Gram stain procedure. Gram negative bacteria have cell walls with a thin layer of peptidoglycan.
all of you are amazing microbiologists
thanks demisew....
guys what are the two acids the skin produce
what are the bacteria's involved in the decaying of food
Enow Reply
Some pathogenic bacteria, such as Clostridium perfringens and Bacillus cereus, are capable of causing spoilage.
Corona has a gray and black cell structure ....if yes explain..if no explain
Joshua Reply
multiple questions and answers in microbiology and bio chemistry
Lakshmi Reply
is the study of a bacteria and other organisms
yes..this book is about bacteria & others organisms
biochemistry is the branch of science that dealing of chemical compounds reactions and other processes
have you any question?
yess, Why scientists not search coronavirus vaccines in short time.
they are on
what are the symptoms for tuberculosis
Most people infected with the bacteria that cause tuberculosis don't have symptoms. When symptoms do occur, they usually include a cough (sometimes blood-tinged), weight loss, night sweats and fever.
symptoms tuberculosis. Fever Chills Night sweats Cough Loss of appetite Weight loss Blood in the sputum (phlegm) Loss of energy
can corona virus transmitted from mother to her child through placenta ?
no,but it can through trait
mutation occur in the genome of corona virus. thats why the corona vaccines forming just difficult
yes coz it's spread through the soft body parts more so the openings in our bodies
what is relation between fear (from covid 19 ) and immune sys ?
because it damages the immune system by reduction the action of WBC
reducing pls
how is it possible for a woman to be pregnant and still See's her period
Prince Reply
we term it as discharge
what is immunity
evans Reply
What is a varuis
A submicroscopic infectious organism, now understood to be a non-cellular structure consisting of a core of DNA or RNA surrounded by a protein coat. It requires a living cell to replicate, and often causes disease
A virus is a biological agent that reproduces inside the cells of living hosts. When infected by a virus, a host cell is forced to produce thousands of identical copies of the original virus at an extraordinary rate
A virus is a microorganism which invade our bodies causing diseases due to eliciting immune responses by the body against it, can replicate using our genome inducing production of proteins helping them to establish new life inside our bodies.
What are the important of capsules
Marriam Reply
what are the roles of male sex hormones
Testosterone is the principal sex hormone inmales and is produced in the testes (testicles). Dihydrotestosterone is a hormonein which the double bond of testosterone has been reduced by enzyrne reactions in the body. ... The testes perform two functions: They produce sperm, and they producetestoster
Capsules in bacteria protect them from phagocytosis of eukaryotic organisms. This is what makes them virulent and harmful without antibodies.
any one told me definition of amoebic dysentery & amoebic liver dysentery?
Amoebiasis, also known amoebic dysentery, is an infection caused by any of the amobae of the Entamoeba group. Symptoms are most common during infection by Entamoeba histolytica. Amoebiasis can be present with no, mild, or severe symptoms. Symptoms may include abdominal pain, diarrhea....
u welcome mira
people explain for me this words in public health.tb prevention 1:promotive 2:preventive 3:curative 4:rehabilitative
Capsules function similarly to endospores they provide an extra layer of protection especially in acidic or basic environments. It is also a thicker membrane which can change the osmosis process and can provides resistance to antibotics depending if it is gram negative or positive.
...As some antibotics focus on breaking down the cell wall and is not able to.
what are the clinical classification of amoxicillin?
how does a autoimmune diso ders develop
Oliver Reply
simply autoimmune disease is not completely understood. There are many variations from genetically inherited to acquired by viruses like HIV. Genetically they may not be prominent until an unknown point in one's life. I am far from an expert, I am just reciting what I have learned. Take rheumatoid
what is anatomy
Mohamed Reply
Anatomy is the study of parts of the human body
the branch of science concerned with the bodily structure of humans, animals, and other living organisms, especially as revealed by dissection and the separation of parts.
Describe the halden effect
The Haldane effect is a property of haemoglobin first described by John ScottHaldane. Oxygenation of blood in the lungs displaces carbon dioxide from hemoglobin which increases the removal of carbon dioxide. This property is the Haldane effect.
Difference between chief cells and parietal cells in the stomach
 Parietal cells are the epithelialcells that secrete HCl and intrinsic factor. They are located in the gastric glands found in lining of fundus and stomach. The gastric chief cells , are cells in the stomach that release pepsinogen and chymosin.
is the study of structure and organs located in human life
listen to Matilda

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