Acquired Immunity and Antibodies

Question 1

What are the differences between nonspecific and specific immunity?

Answer 1

Nonspecifc = innate immune system, does not have memory

Specific = adaptive immune system, has a memory. It also offers improved protection on next exposure, and is the basis for immunity and immunisation

Question 2

What is the role of the innate immune response?

Answer 2

• An immediate knock-down effect that reduces pathogen load
• Part of homeostasis
• Short-lived, no memory
• Innate immune response is to prevent activation of adaptive immunity where possible
• Moduates adaptive response (antigen presentation)

Question 3

What are the characteristics of the antigen-presenting cell (APC)?

Answer 3

• Originates in bone marrow from myeloid / monoblact origins
• Can be tissue derived or blood derived
• Sedentary in epithelium / epidermis
• Migrate to draining lymph node
• Possess a changing phenotype (antigen processing = phagocytic, antigen presenting = non-phagocytic)

Question 4

Provide a brief overview of the acquired immune response / how the alarm is raised?

Answer 4

1. Dendritic cells (APC) travel in lymphatics to lymph node
2. Present antigen to adaptive immune system
3. Lymphocytes differentiate and proliferate in node
4. Return to focus of infection via the blood

Question 5

What are key characteristics of adaptive / specific immunity?

Answer 5

Specificity = pathogen epitopes, every clone of T and B lymphocytes recognises a different antigen

Memory = accelerated and larger responses, fewer checkpoints required for reactivation

Self-limitation = mass apoptosis of lymphocytes in absence of antigen presentation

Question 6

What is humoral immunity?

Answer 6

The process of adaptive immunity manifested by the productionn of antibodies

A key component of acquired immunity:

1. Antibodies = arge, complex proteins that bind foreing molecules termed antigens
2. Capacity to bind potentially millions of different antigens, nature has therefore designed a clever way of producing a diversity of antibodies
3. Think puzzle pieces fitting together correctly, only one will work

Question 7

What are the types and characteristic of the different antibodies?

Answer 7

IgG = Highest opsonisation and neutralisation activities
IgM = Produced first upon antigen invasion, increases transiently 
IgA = Expressed in mucosal tissues and forms dimers after secretion
IgD = UNKNOWN
IgE = Involved in allergy

Question 8

What are the different roles of antibodies?

Answer 8

Bind and inactive toxins
Bind and aggregate antigens / bacteria
Opsonise (makes easier for phagocytes)
Activate complement
In case of IgE, activate mast cells
Antibody dependent cellular cytotoxicity

Question 9

What are the key differences between primary and secondary response?

Answer 9

Magnitude
Primary = smaller, Secondary = larger

Antibody isotype
Primary = usually IgM > IgG, secondary = relative increase in IgG and in certain conditions IgA or IgE

Antibody affinity
Primary = lower than average and more variable, Secondary = higher than average and affinity maturation

Induced by…
Primary = all immunogens, Secondary = only protein antigens