1. Other Cells of Immune System
Dr Shoaib Raza

2. Dendritic Cells Numerous fine cytoplasmic processes
Dendritic cells (Interdigitating)
Potent APC
Present under epithelial cells
Immature dendritic cells are Langerhans cells
Express receptors for capturing microbes
Germinal centers of lymphoid organs
Follicular dendritic cells
Have Fc receptors for IgG

3. Macrophages Phagocytosis APCs and T-Cell activation
Receptors for Fc portion of IgG and C3b, induce humoral immunity

4. Natural Killer Cells Large granular lymphocytes
10-15% of circulating lymphocytes
Part of innate immunity
Kill a variety of tumor cells and virally infected cells without prior sensitization

5. Major Histocompatibility Complex
Responsible for tissue compatibility
Function of MHC is to display peptide fragments of proteins for recognition by antigen-specific T-Cells
Genes present on chromosome 6
HLA or MHC
On the basis of structure, cellular distribution, and function
Class I MHC
Class II MHC

6. Class I MHC Expressed on all nucleated cells and platelets
HLA-A, HLA-B, HLA-C
Heterodimer consists of polymorphic α (heavy) chain, and a smaller nonpolymorphic peptide, β2 microglobulin
Class I molecules display peptides derived from proteins e.g. viral antigen
Recognized by CD8+ T-Cells (cytotoxic T lymphocytes)

8. Class II MHC Expressed in HLA-D HLA-DP, HLA-DQ, HLA-DR
Each class II molecule is a heterodimer consists of α and β chains
Class II MHC present antigens that are internalized into vesicles, and are typically derived from extracellular microbes and soluble proteins
Present antigens to CD4+ T lymphocytes (helper cells)

9. HLA and disease association
Ankylosing spondylitis HLA-B27
Rheumatoid arthritis DR4
Chronic active hepatitis DR3
Primary Sjogren syndrome DR3
Type 1 Diabetes mellitus DR3/DR4

10. Cell Mediated Immunity
Upon antigenic stimulation CD4+ T cells are activated
TH1 IFN-γ IL-12
TH2 IL-4, IL-5 IL-4
IL-13
TH17 IL-17, IL-22 TGF-β, IL-6, IL-1, IL-23