The Immune Process

Macrophages

act as antigen presenting cells and clear immune complexes

Neutrophils

use lytic enzymes to degrade foreign invaders

B-cells

Main function: produce antibodies (humoral immunity)

Clonal Selection Hypothesis: 1. Lymphocyte clones mature in lymphoid organs without antigenic stimulation.

2. Clones are specific for diverse Ags

3. Ags bind to B-cell receptors and 'select' the clone

4. Clonal expansion of selected line

Affinity Maturation:

As more Ag stimulation and clonal selection occurs, antibodies become more specific over time.

T-cells

Main Function: Adaptive Cellular Immunity

Various subsets:

CD4+: Help phagocytes present antigens to the adaptive immune system

CD8+: Directly kill infected/foreign cells

affinity vs avidity

affinity is binding strength

avidity is the overall strength of binding at multiple sites

secondary immune response

amanestic

IL-1

Activates T-helper cells

promotes febrile response

IFN (Interferon) alpha

inhibits viral replication

Tumor necrosis factor (TNF)

kills tumor cells

IL-7 and CSF (colony stimulating factors)

promotes hematopoiesis

blood group systems

There are 29 established blood group systems

Presence is genetically determined

Major antigens include:• Glycoproteins• Glycolipids•

Each antigen has its own unique immunogenecity

HLA

molecules are found on leukocytes and other tissue cells

• Part of the MHC gene system on Chromosome 6

• Three categories or classes of MHC Genes:

• Class I: A, B, and C loci

• Class II: DR, DP, and DQ loc

• Class III: Complement proteins

• These molecules are polymorphic and immunogenic making them critically important for transfusion/transplant of platelets, organs/tissues, bone marrow, and stem cells

in vitro testing

agglutination is the most common method to identify blood groups of donors and recipients

• Agglutination reactions involve two distinct phases:

1. Sensitization: Antigen and Antibody bind

2. Lattice Formation: Collision between antibody coated RBC's

increase serum

increases serum to cell ratio and makes more antibody available to bind

rxn temperature

IgG and IgM best react with Ag at different temps

incubation time

some Ab react best at IS vs having more time to bind to Ag

Low ionic strength solution (LISS)

dilutes Na and Cl ions from blocking Ag-Ab complex formation

polyethylene glycol (PEG)

concentrates the antibody in the test environment

proteolytic enzymes

removes negative charges from rbc membrane making sensitization to remaining Ag easier

zeta potential

For lattice formation to occur antibodies must overcome zeta potential

• Zeta potential \= ionic cloud around RBC

• IgM is easily able to accomplish this

• IgG is not easily able to accomplish this

• Variety of methods help overcome this:

• Centrifugation (forces RBC's together)

• Albumin Potentiator (coats RBC surface)