ImmunologyChapter 3, Lecture 3

• Richard L. Myers, Ph.D.

• Department of Biology

• Southwest Missouri State

• Temple Hall 227

• Telephone: 417-836-5307

• Email: rlm967f@mail.smsu.edu

Mononuclear cells• Monocytes are in the circulation and

macrophages are in the tissues

• Monocytes migrate to tissues and differentiate into macrophages

• Differentiation enlarges monocytes and:– they produces more organelles, – increase phagocytosis, – possess more lytic enzymes– and cause secretion of more soluble factors

Mononuclear cells (continued)• Macrophages may be wandering (motile)

• Others are fixed in particular tissue such as– Kupffer cells in the liver– histiocytes in connective tissue– alveolar macrophages in the lung– mesangial cells in the kidney– microglial cells in the brain

• Macrophages are stimulated by antigen and T cell cytokines

• Possess high levels of class II molecules

Monocyte

Phagocytosis• Macrophages can ingest exogenous

antigens

• Chemotaxis is movement toward substances

• First, macrophages adhere to antigens

• Next, antigens are internalized in phagosomes and are digested by enzymes

• Finally, digested material is released by exocytosis

• Opsonins enhance phagocytosis

Phagocytosis

Antimicrobial and cytotoxic activities of macrophages

• Oxygen-dependent killing– reactive oxygen intermediates– reactive nitrogen intermediates

• Oxygen-independent mechanisms

Resistant pathogens

• Listeria monocytogenes

• Salmonella typhimurium

• Neisseria gonorrhoeae

• Mycobacterium tuberculosis

• Mycobacterium leprae

• Brucella abortus

• Candida albicans

Antigen processing/presentation• Processed antigen appears on the membrane

– macrophages have become “activated”– Ag is associated with class II MHC molecules– called processing and presentation of antigen

• Factors secreted by activated macrophages– Interleukin 1and 6– Hydrolytic enzymes– Interferon alpha and Tumor Necrosis Factor– Complement

Other cells

• Granulocytic cells

• Mast cells

• Dendritic cells– Langerhans cells– interstitual dendritic cells– interdigitating dendritic cells– circulating dendritic cells

Assignment

• Continue to read Chapter 3, Cells and Organs of the Immune System

• Review question 12 and 13 (pg 83)