II - Acquired Immune Response Flashcards
What are the cells and proteins of the acquired immune response?
T & B cells
Antibodies
What makes it different to innate immune system?
Response?
Specificity?
Memory?
Responsive to an unlimited number of molecules.
Able to discriminate between very small differences in molecular structure.
Able to recall previous encounter with an antigen and respond more effectively than the first occasion.
T Lymphocytes
How and where are they formed?
Function?
Stem cells differentiate into pre-T cells. and then mature and proliferate in the thymus. They then circulate in the blood and hang out in the lymph nodes.
Functions - defence against intracellular pathogens and viruses; immunoregulation.
CD4+ T lymphocytes vs CD8+ T lymphocytes:
Function?
which peptides do they recognise?
CD4+ have an immunoregulatory function and are necessary to activate CD8+ and naïve B cells. They produce cytokines and recognise peptides on HLA class II molecules. CD8+ are cytotoxic cells which kill directly. They recognise peptides with HLA class 1 (HLA-A, HLA-B, HLA-C)
B lymphocytes
Where do they arise from?
Function?
Arise from haemopoetic stem cells in the bone marrow.
Mature B cells are mainly found in the bone marrow, lymphoid tissue & spleen.
Further function - long lived memory cells.
Antibody function?
Identification of pathogens
Recruitment of other parts of the immune response: complement, phagocytes, NK
Severe Combined Immunodeficiency: How does it arise? Presenting signs? Commonest form? Levels of T and B cells in blood? Treatment?
Defects in lymphoid precursors of cells (stem cells are still produced but don’t differentiate properly.
Symptoms: unwell by 3 months of age; failure to thrive; persistent diarrhoea; infections of all types; FHx of infant death.
Many causes, but X-linked is the most common form.
There is very low or absent T cells, normal or increased b cells, and poorly developed lymphoid & thymus.
Treatment is prophylactic antis, stem cell transplant, or gene therapy.
NB - NO VACCINATIONS
Why does it take three months post birth for SCID to present?
There is active transport of IgG across the placenta in utero.
Maternal IgG protects the SCID neonate in the first three months of life, after this point in normal children the immune system has matured enough.
DiGeorge Syndrome What is anatomically wrong? Where is the deletion? Symptoms? Lab investigations? Management?
Developmental defect of the 3rd/4th pharyngeal pouch - patients don’t have a thymus.
Deletion is in 22q11.
Symptoms: funny looking; abnormal ears, high forehead, cleft lip & palate, complex congenital heart disease.
Children get recurrent bacterial, fungal & viral infections.
Absent or decreased t cells; normal/high B cells; low IgG, IgA, IgE.
Management - prophylaxis; agresive treatment of infection; T cell function improves with age.
Bruton’s X-linked hypogammaglobulinaemia.
What is it?
Failure to produce mature B cells in the bone marrow, no circulating antibodies after first 6 months.
Selective IgA deficiency.
What is it?
Failure of IgA production - 2/3 individuals asymptomatic, 1/3 get respiratory tract infections.
THIS IS A B CELL DIFFERENTIATION DEFECT.
Common variable immune deficiency.
Blood count?
Symptoms?
Low IgG, IgA, IgE.
Presents with recurrent bacterial infections.
Buzzword –> nitroblue tetrazdium test
Neutrophil
