Basics of Immunology

Question 1

PAMPs

Answer 1

Pathogen-associated molecular patterns. On the intruder,. What is recongnized by PRRs on the cell surface of innate immune cells. These are proteins that humans don’t have, so we know they don’t belong (ie a protein of bacterial cell well or dsRNA)

Question 2

PRRs

Answer 2

Pattern-recognition receptor. Proteins on the cell surface expressed by cells of innate immune system. PRRs identify the PAMPs expressed on foreign intruders

Question 3

TLRs

Answer 3

Toll-like receptors. A type of PRR. There are at least 10 TLRs and are located where infections enter, ie lining blood vessels

Question 4

DAMPs

Answer 4

Damage-associated molecular pattern. Stress or damage indicators expressed by body cells (ie paintball example)

Question 5

What are some foreign patters recognized by TLRs?

Answer 5

TLR1: Lipopeptide (bacterial)
TLR2: Zymosan (fungal)
TLR3: dsRNA (viral)
TLR4: endotoxin
TLR5: flagellin (bacteria)
TLR6: Lipopeptide (mycoplasma)
TLR7: ssRNA (Influenza)
TLR8: ssRNA (viral)
TLR9: Unmethylated CpG (herpes)
TLR10: asthma connection

Question 6

What is the final transcription factor that is most commonly activated by inflammation?

Answer 6

Bad bug makes endotoxin&raquo_space; endotoxin is recognized by TLR&raquo_space; Signal cascade&raquo_space; Activates NF-KB&raquo_space; Inflammation

Question 7

Cytokines

Answer 7

Made by PAMP-stimulated cells. Small cell-signaling protein molecules that are secreted by the immune system for intercellular communication Helps inflammation

Question 8

Chemokine

Answer 8

Made by PAMP-stimulated cells. Family of small cytokines. Induce directed chemotaxis of WBC to site of injury.

Question 9

Innate to Adaptive Immune Response

Answer 9

At the wound site, immature DCs get activated by the cytokines and chemokines secreted by the innate immune response, and they take up anything they can find. Activated (mature) DCs leave the local wound and travel to the nearest lymph node. They “show” the antigen they have eaten to the lymphocytes, and the adaptive immune response develops with T cells, B cells and DCs.

Question 10

Dendritic Cells

Answer 10

Phagocytic cells at the interfaces between the body and the world (skin, lung, mucous membranes…). Immature DCs are the best phagocyte ever! Mature DCs are the best antigen presenting cell ever! (A change in phenotype occurs when the DC matures)

Question 11

T Lymphocytes

Answer 11

Start development in bone marrow, but mature in THYMUS. (Helper) T lymphocytes recognize and remove foreign substances. Two main classes: Helper T cells and Killer T cells.

Question 12

The epic journey of Helper T Cells

Answer 12

They recognize antigens using surface receptors which see antigens presented by the DC that is traveling via lymphatics. When the HTC recognizes the foreign material it becomes activated and proliferates. The daughter cells travel through the body until they reach where the antigen first invaded. There they are re-stimulated and release short-range mediators called lymphokines. These mediators call up much of the inflammatory response, attracting monocytes/macrophages

Question 13

Killer T Cells

Answer 13

Kill any body cell that they identify as containing abnormal molecules. Examine surface of incoming DCs, but they are also looking for fragments on MHC Class I antigen presenter, which are on ALL cells. Appropriate clones of Killer T cells proliferate and daughter cells circulate. When a daughter cell binds a cell showing the same peptide it delivers a lethal “hit” signaling the target cell to commit suicide.

Question 14

The role of B cells in immunity

Answer 14

Recognize and remove foreign substances and protect extracellular spaces of the body by releasing antibodies into tissue fluids, blood, and bodily secretions. They arrange for phagocytosis and recognize antigens via surface receptors and become activated and proliferate. They do NOT require recognition of MHC. Fully differentiated B cells are called plasma cells and are antibody producing “factories”

Question 15

What are the 5 immunoglobulin classes?

Answer 15

IgG, IgM, IgD, IgA, IgE

Question 16

IgG

Answer 16

most abundant antibody, 2 adjacent IgG molecules binding an antigen cooperate to activate COMPLEMENT. It is the only antibody that passes from mother to fetus. Phagocytic cells have receptors for the Fc of bound IgG>Opsonizing

Question 17

Complement

Answer 17

A system of proteins that enhances inflammation and pathogen destruction

Question 18

IgM

Answer 18

Even better at activating COMPLEMENT than IgG. First antibody to appear in blood after exposure to new antigen. Replaced by IgG in 1-2 weeks. It is the ONLY antibody made in the fetus.

Question 19

IgD

Answer 19

Antibody inserted into B cell membranes as their antigen receptor

Question 20

IgA

Answer 20

Most important antibody in secretions (tears, saliva, breast milk). Associated with SECRETORY COMPONANT which makes the antibody resistant to digestive enzymes and plays a role as the first line of defense against microorganisms

Question 21

IgE

Answer 21

Resistance to parasites and worms. Fc attaches to mast cells in tissues. Once attached, when it encounters and antigen it will cause the mast cell to make protaglandins, leukotrienes and cytokines and release its granules which contain mediators of inflammation (ie histamine). Also triggers Mast Cells to release Eosinophils to combat parasites

Question 22

Type I immunopathology

Answer 22

Immediate hypersensitivity. Patient makes too much IgE to environmental antigen

Question 23

Type II Immunopathology

Answer 23

Autoimmunity due to antibodies that react against self. Treat diseases with immunosuppressives

Question 24

Type III Immunopathology

Answer 24

Patient makes antibody against a soluble antigen. Antigen-antibody complex sometimes gets trapped in basement membrane of capillaries, where they activate Complement causing inflammation. (ie Systemic Lupus Erythemtosus and Rheumatoid Arthritis) Also, large doses of penicillin can cause Type III

Question 25

Type IV

Answer 25

T-cell mediated. Can be autoimmune or innocent bystander disease. Example: in TB most of the cavity formation in lungs is T cell mediated, not bacterium mediated

Question 26

AIDS

Answer 26

HIV infection of TH cells; binds to CD4 molecules they have on their surface. Uses reverse transcriptase to insert itself into the cells genome, where it remains latent until T cell is activated, leading to loss of TH cells

Question 27

Chronic frustrated immune response

Answer 27

Antigen is not to "self", but something you can't get rid of, like gut bacteria or gluten

Question 28

Leukocytes

Answer 28

Nucleated cells of the blood, white blood cells. The buffy coat when you centrefuge blood

Question 29

Mononuclear cells

Answer 29

Leukocytes whose nucleus has a smooth outline; monocytes and lymphocytes

Question 30

Polymorphonuclear cells

Answer 30

Cells whose nucleus is lobulated, also called granulocytes because they have prominent cytoplasmic granules; Eosinophils, Basophils and Neutrophils

Question 31

Mast Cells

Answer 31

Granules full of histamine, role in allergy and anaphyaxsis. Very Similar to basphil granulocytes

Question 32

Plasma

Answer 32

Yellow fluid portion of blood in which blood cells are suspended. 55% of blood volume

Question 33

Serum

Answer 33

The clear liquid that does not contain blood cells nor clotting factor. Includes electrolytes, antibodies, hormones, etc

Question 34

What are the central lymphoid organs

Answer 34

Organs where lymphocytes develop: Bone Marrow and Thymus

Question 35

What are the peripheral lymphoid organs

Answer 35

Organs where mature lymphocytes are organized to trap and respond to foreign invaders: lymph nodes, spleen, Peyer's patch and mesenteric lymph nodes

Question 36

Describe the recirculation of lymphocytes from blood to lymph and back.

Answer 36

Lymphocyte in blood encounters the cells lining certain postcapillary venules in peripheral lymphoid tissue. Recirculating lymphocytes may bind to and pass between the endothelial cells into the lymph nodes. Lymph goes to large lymph channels (thorasic duct) >> venous blood >> circulatory loop starts again

Question 37

Antigen

Answer 37

Substance that can be recognized by the immune system

Question 38

Immunogen

Answer 38

An antigen in a form that can give rise to an immune response

Question 39

Antigenic determinant and epitope

Answer 39

small part of a large antigenic molecule, fits into lymphocytes receptor and activates lymphocyte

Question 40

Tolerogen

Answer 40

Antigen delivered in a form, or by a route, which does not give rise to an immune response, and which furthermore PREVENTS an immune response to subsequently administered immunogen which has the same epitopes

Question 41

Lymphocytic Activation

Answer 41

Each lymphocyte has many identical copies of a unique receptor. The antigenic determinant presented by Dendritic Cell fits into a particular lymphocyte receptor. To activate a T or B cell, the fit between receptor and antigen must be good enough and several nearby receptors must be simultaneously bound by antigen as well. (MHC must also be involved for T-cells to be activated).

Question 42

What are the receptors of T and B cells composed of?

Answer 42

T cells: alpha and beta chains | B cells: samples of the antibodies that the cell will eventually secrete

Question 43

Humoral Immunity

Answer 43

Antibody mediated response, occurs extra-cellularly where all the bacteria live. B lymphocytes are the main cell involved. B cells transform into plasma cells which secrete antibodies.Cytokines are also released. Can be transferred by serum.

Question 44

Cell Mediated Immunity

Answer 44

T lymphocytes become activated. These in turn activate macrophages, NK cells, and cytotoxic T lymphocyte. Cytokines released when T cells become activated. Not transferred by serum

Question 45

H chain

Answer 45

Heavy chain of antibody. Each antibody has 2 H-chains, each H chain has 1 variable domain (VH) and 3-4 constant domains (CH1, CH2, CH3, (CH4)), 5 kinds of H chains (gamma, alpha mu, epsilon, delta) each corresponds to the appropriately named antibody: IgA has alpha chains

Question 46

L Chain

Answer 46

Light chain of antibody. Each antibody has 2 L-chains, each L chain has 1 variable domain (V1) and one constant domain (C1)

Question 47

Kappa and Lambda Chains

Answer 47

2 varieties of L chain, each cell that makes an antibody has a CHOICE, but uses ONLY ONE kind

Question 48

Hinge Region

Answer 48

Allows for flexibility so that when bound to an antigen, the constant part of the antibody can change conformation

Question 49

Fab

Answer 49

S-S bond between H chains fully reduced

Question 50

F(ab')2

Answer 50

2 Fabs still joined by S-S bond

Question 51

Fc

Answer 51

Non-antigen binding region of the antibody, makes antibody participate in complement

Question 52

Complementarity-determining Regions (CDRs)

Answer 52

Light chain and heavy chain variable region is NOT uniformly variable, most of the variability is in the 3 regions called hyper-variable regions of CDRs, amino acids in this region comprise the actual antigen-binding site

Question 53

Hypervariable Regions

Answer 53

Areas on the variable region of light/heavy chain with amino acid availability

Question 54

Variable (V) Domain

Answer 54

A the N-terminal of the antibody, differences in amino acid sequences between antibodies of different specificites

Question 55

Constant (C) Domains

Answer 55

Region that is essentially identical on the antibodies, made up of compact, structurally similar domains called C domains

Question 56

Characteristic chains of IgG

Answer 56

2 light and 2 gamma (heavy)

Question 57

Characteristic chains of IgE

Answer 57

2 light and 2 epsilon (heavy)

Question 58

Characteristic chains of IgD

Answer 58

2 light and 2 delta (heavy)

Question 59

Characteristic chains of IgA

Answer 59

4 light 4 alpha (heavy), 1 Joining chain and 1 Secretory component (creates a dimer)

Question 60

Characteristic chains of IgM

Answer 60

10 light, 10 mu (heavy) and 1 Joining chain (creates a pentamer)

Question 61

Name immunoglobin classes from smallest to largest

Answer 61

IgG < IgE < IgD < IgA < IgM

Question 62

Combining Sites

Answer 62

Where the antibody binds to the antigen and is made up of the V domains of both the H and L chain

Question 63

Subclass of Immunoglobins

Answer 63

Immunoglobins are dived into subclasses because of slight differences in the amino acid sequences of their H chain C regions

Question 64

Allotypes of Immunoglobins

Answer 64

Minor allelic differences in the sequence of immunoglobins between individuals, determined by allotypes of your parents, useful in determining relatedness

Question 65

Idiotypes of Immunoglobins

Answer 65

Unique combining region, made up of CDR amino acids of its L and H chain, that each antibody has, Anti-idiotypes are antibodies made that recognize the unique sequence of that combining site.

Question 66

Valence

Answer 66

The valency of an antibody refers to the number of antigenic determinants that an individual antibody can bind. The valency of all antibodies is at least two (divalent) and in some instances more (multivalent)

Question 67

Affinity

Answer 67

The strength with which and antibody molecule binds to an epitope

Question 68

Precipitation

Answer 68

Large Immune complexes that are formed at or near equivalence tend to become insoluble and fall out of solution. When the antigen is a molecule, it is called precipitation

Question 69

Agglutination

Answer 69

Large immune complexes that are formed at or near equivalence tend to become insoluble and fall out of solution. When the antigen is a cell or cell-sized particle, it is called agglutination.

Question 70

Epitope

Answer 70

The part of the antibody that actually interacts with the antigen, usually 10-20 amino acids long. Also known as antigenic determinant. Proteins have several epitopes which bind to different antibodies

Question 71

Why does a line of precipitate may form in agar gel when antigen and antibody diffuse towards each other

Answer 71

Precipitate forms in the agar when the antigen and antibody meet at optimal proportions (more immune complex forms and precipitates out of solution). This is called immunodiffusion

Question 72

Lectin Pathway

Answer 72

Part of INNATE IMMUNITY. Mediated by mannose-binding protein (MBO or MBL), a lectin. MBP binds certain mannose-containing structures found in carbohydrates of bacteria but not humans. MBP is similar to C1q so the lectin pathway goes: 4-2-3-5-6-7-8-9

Question 73

Classical Pathway

Answer 73

Activated by complexes of IgG or IgM antibody with antigen. Fc portion of antibodies change which allows binding and activation of C1q. C1q must interact with the 2 Fcs simultaneously. Pathway goes: 1-4-2-3-5-6-7-8-9. Activating C3 and C5 is part of compliment because they are responsible for opsonizing, chemotaxis and anaphylastoxic

Question 74

Alternative Pathway

Answer 74

Part of Innate Immune response. Activated by IgA-antigen complex. Bacteria must activate C this way even in the absence of antibody. Complement activated by C3. IgA and cell wall structures provide a surface of binding C3b and factor B, properin and factor D, which can activate C5 (and thus C6-7-8-9)

Question 75

Oponizing

Answer 75

C3b adheres to membranes. Phagocytic cells have C3b receptors and so they get a firm grip on an antigen if opsonized with C3b. IgG is also opsonizing because phagocytes have receptor for its Fc end called FcR

Question 76

Lytic

Answer 76

If the membrane attack complex is activated when C5 activates C6-7-8-9. C8 and C9 form a lesion on the target cell membrane. Cell loses ability to regulate osmotic pressure and lyses

Question 77

Anaphylatoxic

Answer 77

C3a, C4a and C5a can all release histamine from mast cells by binding. This leads to and increase in blood flow to the area and a better chance for inflammatory cells to get out of blood and into tissues

Question 78

Chemotactic

Answer 78

The C5 activation product, C5a, is chemotactic for phagocytes, especially neutrophils

Question 79

Toxoid

Answer 79

Bacterial toxin (usually endotoxin) whose toxicity has been weakened or suppressed either by chemical (formalin) or heat treatment

Question 80

Cross-reactivity

Answer 80

The tendency of one antibody to react with more than one antigen (ie immunize a person with cow pox, the antigenic determinant of small pox will also be recognized and the person will be immunized)

Question 81

Low affinity B cell binding

Answer 81

B cells are typically activated when the antigen binds to B cell receptor and if the binding is strong enough, the B cell will be activated. If the binding is low affinity, the B cell is not activated but if another antigen comes along which binds AND activates, then the product of the cell (secreted antibody) may combine with the low affinity antigen well enough to be "inconveneint" (ie rheumatic heart disease)

Question 82

Clonal Selection Theory

Answer 82

Each cell of the immune system is programmed to make only one antibody. The choice of which antibody a cell makes is RANDOM. When it encounters a lymphocyte whose receptors bind it with a high affinity, the lymphocytes is activated and makes clones and antibodies. The best fitting clones are SELECTED by the antigen (Think K-mart example)

Question 83

Look at the diagram of heavy and light chain gene regions of human DNA

Answer 83

Okey dokey!

Question 84

Class switching

Answer 84

Single mature B cell starts by making IgM and IdD. Later, it may switch to IgG, IgE or IgA. In all cases, the V domain stays the same but the C region of the H chain changes. A cell can switch heavy chain, but cannot switch light chains. Switching classes involving excising of the gene cannot go back to the original class.

Question 85

Hypermutation

Answer 85

Each time a B cell divides after antigenic stimulation, there is a good chance 1 of the daughter cells will make a slightly different antibody, leading to mutants that are better (or worse) affinities during immune response

Question 86

N-region Diversity

Answer 86

Created by the sloppiness of V-D and D-J joining. 1)Exonucleases chew away a few nucleotides after the DNA is cut but before the gene segments are joined. 2)Enzyme TdT adds nucleotides WITHOUT A TEMPLATE. Lots of diversity produced, but the price is that frame shift mutations occur frequently. VDJ region is the most mutable out of the whole genome!

Question 87

So, you will look at the diagram in the notes, but what ware some basics about the heavy and light genes

Answer 87

Variable domain is made of V, D, J for heavy chains (Light chains ONLY have V and J). One random D (1 to n) is brought to one random J (1 to n) and the intervening DNA is excised. Then V is brought to D-J and the intervening DNA is excised. After VDJ is put together, a primary RNA transcript is made, from just left of the chosen V all the way through the right of the Delta constant region gene. The primary transcript is alternatively spliced to make VDJmu and VDJdelta, for example. (The D goes between the VJ when its Hot and Heavy)

Question 88

Why do we write V(D)J instead of VDJ?

Answer 88

The variable domain region of heavy chains is composed of V, D, and J. The variable region of the light chain are only composed of V and J segments.

Question 89

Th1 Cells, and Downstream affects

Answer 89

Circulate until encounters antigen. Secrete lympohkines (INTERFERON GAMMA), which is chemotactic for monocytes and macrophages and turns them into ANGRY macrophages. The macrophages release their own cytokines (TNF and IL-1) that increase inflammation

Question 90

Th17 cells

Answer 90

Make pro-inflammatory lymphokine IL-17. Main job is inflammation, and make EVEN ANGRIER macrophages. Implicated in several autoimmune diseases.

Question 91

Th2 cells

Answer 91

Circulate through blood until discovering antigen. Secrete IL-4 and IL-3 which attract and activate macrophages involved in HEALING.

Question 92

Cytokine secreted by Th1 cells

Answer 92

Interferon Gamma- pro imflammatory and chemotatic for macrophages and monocytes, creating ANGRY macrophages

Question 93

Cytokine secreted by Th17 cells

Answer 93

IL-17- inflammation and makes even even ANGRIER macrophages

Question 94

Cytokine secreted by Th2 cells

Answer 94

IL-4 and IL-3, attracts and activates macrophages. IL-4 is Chemotatic for eosinophils and pushes B cells to switch from IgM/IgD to IgE (antibody for parasites and allergies)

Question 95

What does T cell sibling rivalry mean?

Answer 95

A balance between Th1 and Th2. IFN gamma (made by Th2) suppresses Th2 differentiation. IL-4 (made by Th2) suppresses Th1

Question 96

Follicular helper T cells (Tfh)

Answer 96

Are activated by DC in lymph node, then migrate to follicles of cortex where B cells are present. Tfh secrete cytokines and direct B cells to switch from IgM to IgG, IgE, or IgA

Question 97

Regulatory T Cells (Treg)

Answer 97

Suppress the activation and function of other T helper cells. Most are CD4+/CD5+. Can suppress 1000 Th cells

Question 98

What cytokines are produced by Treg?

Answer 98

TGFbeta and IL-10. Suppresses Th cells

Question 99

Cytotoxic Killer T cells (CTL)

Answer 99

Signals target cells to commit suicide

Question 100

How to CTLs induce a cell to apoptos?

Answer 100

1. Activate Fas (CD95) "death receptor" on target (CTLs have Fas ligand, CD95L) 2. Secrete contents of lytic granules which contain proteases called granzymes and perforins that allow penetration into target cell

Question 101

What are the surface markers that can distinguish T and B cells?

Answer 101

T cells have CD2, CD4 and CD8 (different T cells have different markers; see further cards). B cells have antibody surface markers. Specific surface marker CD20

Question 102

What cells have CD3 surface marker?

Answer 102

virtually all T cells

Question 103

What cells have CD4 surface marker?

Answer 103

Th2, Th1, Treg cells

Question 104

What cells have CD8 surface marker?

Answer 104

CTL cells

Question 105

Define Lymphokine

Answer 105

short range mediators made by lymphocyte that affects behavior of the same or another cell. A subset of cytokines. Examples: IL-2, IFNgamma, IL-4, IL-5, IL-10

Question 106

Define Chemokine

Answer 106

Small, short range mediators made by any cell that causes inflammation. Examples: MIP-1 to -4, CCL28

Question 107

Define Cytokine

Answer 107

short range mediators made by any cell that affects behavior of the same or another cell. Examples: IL-1, TNFalpha, IL-12

Question 108

What is a mitogen?

Answer 108

A protein that stimulates T cell division. They don't actually bind to the antigen-binding site on T cell. Instead it binds to the CD3 domain that controls signal transduction. Examples: PHA (binds CD3), pokeweed mitogen

Question 109

Mitogen vs Antigen

Answer 109

Antigens are specific, Mitogens are nonspecific.

Question 110

Specifics of T cell receptors

Answer 110

Made of 2 chains, alpha and beta. Each chain has common and variable portion. Receptor is made out of V,(D),J recombined and each chain has 2 CDRs (takes place in thymus). Both alpha and beta chains have trans-membrane domains (picture parallel lines as receptor)

Question 111

Specifics of B cell receptors

Answer 111

Bind antigen directly with surface antibodies. Receptors made of V,(D),J regions and recombination. Made of 2 heavy and 2 light chains, with constant and variable regions (picture y-shaped receptor)

Question 112

Class I Mediators

Answer 112

All nucleated cells have MHC Class I on their surfaces. Class I is recognized by CTLs. "Look what I've been making!"

Question 113

Class II Mediators

Answer 113

Class II products are only on dendritic cells, macrophages and B cells. Recognized by Th. "Look what I've been eating!".

Question 114

Characteristics of T-independent antigens

Answer 114

Have the same epitope repeated over and over, common in carbohydrates. The carbohydrate chain binds to the B cell antibodies, activating the cell to diving. The response is almost all IgM

Question 115

Journey of a T cell

Answer 115

Bone Marrow...(Pre-T cells)...Stroma of Thymus....Divide and rearrange V(D)J, changing from CD4-/8- to 8+/4+. In the Thymus, T cells display CD1 surface marker....A T-cell that binds with high-affinity to peptide in the thymus dies. Also, cells with no affinity (to the MHC) also die. The ones that survive are ones what bind MHC but NOT the peptide!

Question 116

How is it that the T cells can be exposed to numerous body peptides will stuck in the Thymus?

Answer 116

AIRE! A gene that upregulates body genes so peptides can be loaded to MHC for T cell selection

Question 117

What are the phases of developing B cells?

Answer 117

Pro B cell...Pre B cell...Immature B cell...Mature B cell

Question 118

Pro B cell

Answer 118

Progenitors that are identifiable when they begin to made detectable cytoplasmic mu chains

Question 119

Pre B cell

Answer 119

A cell with cytoplasmic IgM but no surface IgM

Question 120

Immature B cell

Answer 120

A cell with surface IgM only and can interact with outside world. If immature B cell is exposed to antigen, the signal causes the cell to try receptor editing. If unsuccessful, cell will die (clonal abortion)

Question 121

What is clonal abortion/deletion?

Answer 121

Pre-B cells are differentiating into immature B cell and any cell whose receptor happens to be anti-self will almost surely encounter "self" in the bone marrow. If so, it will be destroyed. If it does not encounter an antigen in the marrow (cell is not anti-self), then it will mature further to slgM and slgD.

Question 122

Mature B cell

Answer 122

A cell with both IgM and IgD are on the cell surface. Present in the lymph nodes

Question 123

Know that sIgD appears on mature B cell 24 hours after sIgM

Answer 123

Ok

Question 124

What is the antibody response to a typical antigen in a primary and secondary response?

Answer 124

During primary B cell response to antigen, IgM is secreted first, then helper T cells help B cells switch to IgG (or IgA or IgE). Remember that after its switched from IgM, it cannot go back because the "mu" and "delta" have been spliced out!

Question 125

What is the antibody response to secondary (booster) immunizations?

Answer 125

IgM response is the same as in primary, but the IgG response (helped by T cells) is sooner, faster and higher and more prolonged because of immunological memory

Question 126

Whats up with a baby's immune system?

Answer 126

IgM is made by fetus before birth. IgG is from the mother, and takes a huge spike ~6 months gestation and babies have 100% adult levels are full-term. Therefore, premature baby has low IgG (and lower than normal IgM). Half-life of IgG is 3 weeks, so the level from mother is depleted by 10 months. That ok though, because infants start making their own at about 3 months of age.

Question 127

Are kids born with compliment?

Answer 127

Yup.