Content:

 Antibody
1. Ab structure
Gamma-globulins (Igs), although some Igs are not gamma globulins and vice
versa.
Are soluble glycoproteins that recognized Ags.
Mass of Ig monomer: 150kDA (kilo Dalton)  considered average size molecule
5 class of Abs:
a. IgM: first Ig created, low specificity
b. IgG
c. IgA
d. IgD
e. IgE
CH4 only at IgE and IgM.

2. Function
NOC – neutralization, opsonization, C’ activation
Neutralization:
 Antitoxin (Ab) neutralize bacterial toxins, viruses
 Antitoxin is developed actively as a result of:
 Previous infection
 Artificial immunization
 Transferred passively as antiserum (Anti-venom)
Opsonization and Complement activation
 act as opsonins (Ab) and enhance phagocytosis; Clump
 bacteria (agglutination) leading to phagocytosis
 prevent the adherence of microorganisms to their target cells,
 e.g. IgA in the gut
 Activate the complement and lead to bacterial lysis.

3. Diversity
7 mechanisms for generation of Ab diversity
i. Multiple germline V genes
ii. VDJ and VJ recombinations (RAG-1; RAG-2: Somatic
iii. recombination)
iv. N-Nucleotide addition (TdT)
v. Gene conversion
 vi. Recombinational Inaccuracies (imprecise joining)
vii. Somatic point mutation (AID)
viii. Assorted H and L chains

 Complement
1. Definition
Complement system is “a key innate immune effector system” consisting of over
30 proteins (nine components) produced by the liver and found in circulating
blood serum, tissue fluids.
Terminology:
Complement proteins are often (in classical pathway) designated by an uppercase
letter C followed by numbers based on the order in which they were identified
and are inactive until they are split into products.
Functions:
 Cytolysis
 Opsonization, virus neutralization
 Inflammation/ chemotaxis of immune cells (chemoattractants/ chemokines)
 Portions of the C’ system contribute to immune adherence, anaphylatoxin
formation and other physiological functions

2. Roles
a. Direct Microbial killing/ cytolysis
b. Chemotaxis
c. Triggering and amplification of Inflammation
d. Cellular activation
e. Opsonization and clearance of immune complex
f. Development of Ab response

3. Active pathways and active components

3 pathways – Classical, MB-lectin, Alternative

Classical:
C1 – Recognition Unit
C1 consists of 3 subunits: C1q, C1r, and C1s.
C1q molecule consists of a collagenous region with six globular head groups globe
end serves as recognition unit.
When Ab binds to Ag, binding sites for the globular head groups of C1q are
exposed on the Fc region of the Ab.
Activation Unit:
Order of activation: C1, C4, C2, C3, C5
C1s cleaves C4 into C4a and C4b
C1s cleaves C2 into C2a and C2b
C4b2a = C3 convertase, is enzymatically active and can cleave many molecules of
C3 into C3a and C3b.
C4bC2a3b= C5 convertase, bind C5, present it for cleavage by C2a into C5a,
C5bC4b2a3b5b: Activation unit

Lectin
Mannose(an)-binding lectin (MBL)
Triggered by microbial carbohydrates: Mannose, N-acetyl glucosamine
Instead of C1 complex, it started with complex- MBL/MASP:
 MBL- mannan binding lectin, a C1q-like recognition unit
 MASP: MBL-associated serine proteases which work like C1s

Alternative
Cleavage of C3 and activation of the remainder of the complement cascade occurs
independently of Ab.
Molecules of C3 undergo cleavage at continuous low level in normal plasma (tick-
over status).
Triggers for the alternative pathway include:
 bacterial cell walls
 bacterial lipopolysaccharides (LPS)
 fungal cell walls
 some virus infected cells
 rabbit erythrocyte.
At least 4 serum proteins including factor B, factor D, properdin (P), and initiating
factor (IF) function in this pathway.
C3b attaches to appropriate site (activating surface) which is actually a protective
surface
Action by the 4 serum proteins on C3b proceeds to the C3 activator stage without
participation of C1, C4 or C2.
Activation sequence: C3, C5, C6, C7, C8, C9.

4. Regulation
Modulating mechanisms are necessary to regulate complement activation and
control production of biologically active split products.
4.1. First means of control is extreme lability of activated complement
 If activated complement does not combine within milliseconds the activity
is lost or decreased.
 Active fragments rapidly cleared from the body.
4.2. Second type of control involves specific control proteins
 C1 inhibitor (C1inh) remove C1r and C1s from C1 complex or remove MASP
from MBL complex. It is a serin protease inhibitor/ serpin called C1inh.
 Complement Factor I (fI) is a protein of the complement system, regulates
complement activation by cleaving cell-bound or fluid phase C3b and C4b.
 A number of proteins act to control membrane attack unit, eg. CD59.
 CCP: regulators of complement activation (RCA) or complement control
proteins (CCP).

 Cells of the Immune System

Origin of Cells of Immune System:
Derived from common progenitor cell in bone marrow
– Pluripotent hematopoietic stem cell
Progenitor Stem Cells
1. Erythroid lineage
• Erythrocytes and Megakaryocytes (→platelets)
2. Myeloid lineage
• Monocyte/macrophage, Dendritic cells, PMN’s, mast cells
3. Lymphoid lineage
• Small and large lymphocytes
5 types of immune cells:
1. Neutrophils
2. Eosinophils
3. Basophils
4. Monocytes
5. Lymphocytes
Granulocytes – neutrophils, eosinophils, basophils
Large granular lymphocyte – Natural Killer (NK) cells.
B cell  plasma cell
“Eaters” – macrophage, neutrophils
  Tissue and Organ of the IS.
Lymphocytes originate in bone marrow.
Central vs Peripheral lymphoid organs and tissues
1. Central: production and development of lymphocytes
Bone marrow (B cells) and Thymus gland (T cells)
Pro-Pre-Immature-Mature
B and T cells migrate to and function in 2nd lymphoid organs and tissues.
2. Peripheral: mature lymphocytes meet pathogens
Spleen, adenoids, tonsils, appendix, lymph nodes, Peyer’s patches (or MALT at
intestine), mucosa-associated lymphoid tissue (MALT)
Spleen – remove damaged RBCs, activates lymphocytes in reacting to blood-borne
pathogens
Lymphatic circulation: maintain fluid balance in the body by collecting excessive
fluid and matter from tissues
1. Lymphatic vessels:
 Collect and return interstitial fluid to blood
 Transport immune cells throughout body
 Transport lipid from intestine to blood
2. Lymph nodes:
 Kidney-shaped organs at intervals along lymphatic vessels
3. Brain:
Lack of lymphatic drainage
Tissue grafted into the CNS sparks less hostile response  blood-brain barrier

1: 20 points: Blood group and ABO Blood group

1. Blood group:
 RBC membranes have glycoprotein Ags on their external surfaces.
 Ags that promote agglutination are known as Agglutinogens.
These Ags are:
 unique to the individual
 promoters of agglutination and are referred to as agglutinogens
 recognized as ‘foreign’/non-self if transfused into another individual

2. ABO Blood group:

a. Structure:
  H antigen is controlled at the H locus on chromosome 19.
 Individuals with the rare Bombay phenotype (hh) do not express antigen H
on their red blood cells
ABO antigen is controlled by I locus on chromosome 9
 IA: encodes a glycosyltransferase that bonds α-N-acetylgalactosamine (NAC)
to the D-galactose end of the H antigen  the A antigen.
 IB: encodes a glycosyltransferase that bonds α-D-galactose to the D-
galactose end of the H antigen  the B antigen.
 IO: mutated gene, no product
4 main phenotypes: A, B, AB, and O.
Blood Group Antigens on RBCs Antibodies in Genotypes
Serum
A A Anti-B AA or AO
B B Anti-A BB or BO
AB A and B Neither AB
O Neither Anti-A and Anti-B OO
 AB is considered the universal receiver type, whereas O is the universal
donor type.

b. ABO Compatibility:
Immune reaction can occur if two different and non-compatible blood types are
mixed together:
• Surface antigens can act as immune system triggers.
• Blood types must be matched to avoid an ABO incompatibility reaction.
• Important when a patient needs to receive BLOOD (TRANSFUSION) or
have an ORGAN TRANSPLANT.

2: 20 points: Understanding CBC with Diff Report

CBC, also known as Complete Blood Cell Count, is a blood test that provides
important information about the types and quantities of different cells present in
your blood.
Erythrocytes (RBC): 4.0 to 5.4 (M/uL)
Thrombocytes (Platelets): 145 to 400 (K/uL)
Leukocytes (WBC): 4.8 to 10.8 (K/uL)
Neutrophils: 40 to 74 %
Band neutrophils: 0 to 9
Eosinophils: 0 to 6
Basophils: 0 to 1
Lymphocytes: 15 to 47
Monocytes: 0 to 12

Hematocrit is the ratio of the packed cells to total volume.

After centrifugation, the tube containing blood has 3 layers – plasma (water,
proteins, nutrients, etc.), buffy coat (WBCs, platelets), and hematocrit (RBCs).

To calculate the hematocrit, we measure the height of the RBC layer relative to
the volume of the blood in the tube.
1. Normal blood – 37% - 47% (male); 42% - 52% (female)
2. Anemia – depressed hematocrit%
3. Polycythemia – High hematocrit%

3: 20 points: Understanding on Rhesus Blood Type

a. General information:
 Antigen discovered in the Rhesus monkey.
 Rh is an Ag on RBC
 Rh blood type refers to the presence/ absence of the Rh agglutinogens on
RBCs indicated as Rh+/Rh- blood type.
 There are 45 different types of Rh agglutinogens.
 Common: C, D, and E
b. Rh Antigens:
 D antigen is the most common and most immunogenic
 Approximately 80-85% Caucasians have D antigen
 Individuals lacking this allele are called “Rh-negative”
 Only develop antibodies against the D antigen after exposure
(transfusion/pregnancy)
c. Rh Antibodies:
 IgG class of immunoglobulins
 Lack capacity to bind complements
 Hemolysis does not occur after 1st transfusion with Rh factor but it occurs
in later transfusions; this is due to the immune response that develops
upon exposure to the Rh antigen.