Granuloma

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Infectious granuloma of the hand caused by Mycobacterium marinum from an employee in a tropical fish shop
Odontogenic, radicular granuloma on a freshly extracted tooth

A granuloma (from the Latin granulum 'grain' ) is a nodular collection of the phagocytes of the immune system ( macrophages ). A granuloma can contain other cells: epithelial cells and multinucleated giant cells are descendants of macrophages, and lymphocytes , granulocytes and fibroblasts can also be involved in the formation of granulomas. Some granulomas develop a capsule of connective tissue (fibrosis), others have necrosis in their center .

Granulomas occur when the macrophages cannot break down a noxious substance (e.g. bacteria , parasites or foreign bodies ), which creates a chronic inflammatory stimulus. The purpose of the granuloma is to encapsulate the alien invader and prevent it from spreading further. In addition, pathogens can be combated more effectively through a local concentration of lysosomal enzymes and bactericidal substances.

In diagnostics, the size and tissue structure of the granulomas allow conclusions to be drawn about the underlying trigger.

Granuloma cells

The following cells can be found in a granuloma:

  • Macrophages are the cells that form the granuloma from the start and can therefore always be found in it. Their task as "phagocytes" is to eat ( phagocytize ) particles, bacteria and cell debris , and to break them down and to present parts of what has been eaten to other immune cells, which may initiate a greater immune response.
  • Epithelial cells can develop from the macrophages of the granuloma after a few days. They are firmly interlocked with one another and are reminiscent of epithelial cells . There are two types of epithelial cells: one is highly active in phagocytosis and kills microbes; the other does not phagocytose, but is secretory and could play a supporting role in the function of the granuloma. It is unclear what the decisive factor behind the transformation of normal macrophages into epithelial cells is. In the case of foreign body granulomas, it could depend on how long the foreign substance has been in the body, i.e. epithelial cells form when the macrophage granuloma takes too long to break down the foreign body or substance. However, different foreign substances seem to stimulate the immune system differently, for example oak pollen does not lead to the formation of epithelial cells, but pine pollen does. Infectious granulomas, on the other hand, are practically always epithelial cells.
  • Multinucleated giant cells are very large cells with several cell nuclei that are also derived from macrophages. Classically, a distinction is made between multinucleated giant cells with cores arranged in the shape of a horseshoe (Langhans cells) and those with unordered cores. The ordered Langhans cells occur in tuberculosis granulomas, while disordered giant cells are typical for foreign body granulomas. The two forms of multinucleated giant cells can merge into one another. Their function is not entirely clear. It appears that their ability to eat foreign objects is highly dependent on the inflammatory environment. This explains why they can phagocytize much better than normal macrophages in some studies, while they were significantly worse in other studies. For a long time it was assumed that multinucleated giant cells arise exclusively from the merging of macrophages. However, there are indications that multinucleated giant cells can well arise from individual macrophages.

In addition to the phagocytes and their descendants, a number of other cells can be involved in a granuloma, including lymphocytes and fibroblasts .

Classification and occurrence

Granulomas can be classified according to various criteria, for example according to their cause (infectious versus non-infectious granulomas) or their cell composition. In the latter case, the distinction between epithelial cellular granulomas and histiocytic granulomas is common. Epithelial cell granulomas are sharply demarcated nodules with densely packed epithelial cells. Histiocytic granulomas, on the other hand, are rather vaguely delimited collections of tissue macrophages. Both groups are further subdivided.

Epithelial cell granulomas:

  • Small-sized accumulations of epithelial cells (“sarcoid-like lesions”): they are found in lymph nodes in the drainage area of ​​solid tumors , in various lymphomas and in toxoplasmosis.
  • Sarcoid type: mostly small accumulation of epithelial cells with ordered and disordered giant cells. On the outside there is a connective tissue capsule from which runners can grow towards the center. Central necrosis are rare. (Formation Granulomas 2018) This type of granuloma is found in sarcoidosis, Crohn's disease and primary biliary cholangitis as well as in response to beryllium (see Chronic beryllium disease ), aluminum and organic dust.
  • Tuberculosis type: Appearance similar to granulomas of the sarcoid type, the main difference is a central "caseating" necrosis , the appearance of which is reminiscent of soft cheese. There is a wall of lymphocytes around the granuloma. Tuberculosis-type granulomas are mainly caused by infections with bacteria that invade cells and multiply there (intracellular pathogens). These include infections with mycobacteria (tuberculosis, leprosy) and syphilis .
  • Pseudotuberculosis type: rather indistinctly limited collections of macrophages and epithelial cells. In the center there are dead (necrotic) granulocytes , this is called the "central microabscess". Occurrence in infections with Yersinia pseudotuberculosis , cat scratch disease , lymphogranuloma venerum , rabbit plague , fungal infections, various parasites.

Histiocytic granulomas:

  • Rheumatoid type: granulomas up to 3 cm in size from tissue macrophages (histiocytes). They contain a central necrosis and are surrounded by connective tissue on the outside. Granulomas of the rheumatoid type occur as "rheumatoid nodules" in rheumatoid arthritis , as well as in granuloma annulare in the context of diabetes mellitus and in various skin diseases.
  • Rheumatic type: with rheumatic fever , granulomas occurring mainly in the heart muscle with central necrosis (Aschoff's node). The macrophages involved have some peculiarities in their appearance, which is why they are called "Anitschkow" and "Aschoff cells".
  • Foreign body type: mainly disordered giant cells that can become very large. In between, immigrated macrophages, around them lymphocytes, fibroblasts and sprouting capillaries . They form as a reaction to various substances and particles that are endogenous (crystals: urate, cholesterol. Others: horny lamellae, mucus, necrotic fatty tissue) and foreign (sutures, wood splinters, thorns, stone and metal dust, endoprosthesis abrasion, silicone oil from breast implants) can.

Individual evidence

  1. ↑ Entry on granuloma in Peter Altmeyer's Encyclopedia (online) Springer Verlag, 2017
  2. ^ Antonio J. Pagán, Lalita Ramakrishnan: The Formation and Function of Granulomas . In: Annual Review of Immunology . tape 36 , no. 1 , April 26, 2018, ISSN  0732-0582 , p. 639-665 , doi : 10.1146 / annurev-immunol-032712-100022 .
  3. ↑ Hans-Hartmut Peter, Ursus-Nikolaus Riede: Chapter 5, Disorders of the preservation of individuality. In: Riede, Werner, Schäfer (Ed.): General and special pathology. 5th edition. Thieme, Stuttgart 2004. p. 226
  4. ↑ Müller, Höfler, Imhof, Holländer: Chapter 3, inflammation. In: Böcker, Denk, Heitz, Höfler, Kreipe, Moch: Pathology. 5th edition. Urban & Fischer, Munich 2012, p. 69
  5. ↑ Hans-Hartmut Peter, Ursus-Nikolaus Riede: Chapter 5, Disorders of the preservation of individuality. In: Riede, Werner, Schäfer (Ed.): General and special pathology. 5th edition. Thieme, Stuttgart 2004, p. 227
  6. ^ Antonio J. Pagán, Lalita Ramakrishnan: The Formation and Function of Granulomas . In: Annual Review of Immunology . tape 36 , no. 1 , April 26, 2018, ISSN  0732-0582 , p. 639-665 , doi : 10.1146 / annurev-immunol-032712-100022 .
  7. ↑ Müller, Höfler, Imhof, Holländer: Chapter 3, inflammation. In: Böcker, Denk, Heitz, Höfler, Kreipe, Moch: Pathology. 5th edition. Urban & Fischer, Munich 2012, p. 69
  8. ↑ Hans-Hartmut Peter, Ursus-Nikolaus Riede: Chapter 5, Disorders of the preservation of individuality. In: Riede, Werner, Schäfer (Ed.): General and special pathology. 5th edition. Thieme, Stuttgart 2004. p. 230
  9. ↑ Müller, Höfler, Imhof, Holländer: Chapter 3, inflammation. In: Böcker, Denk, Heitz, Höfler, Kreipe, Moch: Pathology. 5th edition. Urban & Fischer, Munich 2012, p. 69
  10. ↑ Hans-Hartmut Peter, Ursus-Nikolaus Riede: Chapter 5, Disorders of the preservation of individuality. In: Riede, Werner, Schäfer (Ed.): General and special pathology. 5th edition. Thieme, Stuttgart 2004. p. 230
  11. ↑ Müller, Höfler, Imhof, Holländer: Chapter 3, inflammation. In: Böcker, Denk, Heitz, Höfler, Kreipe, Moch: Pathology. 5th edition. Urban & Fischer, Munich 2012, p. 69
  12. ↑ Hans-Hartmut Peter, Ursus-Nikolaus Riede: Chapter 5, Disorders of the preservation of individuality. In: Riede, Werner, Schäfer (Ed.): General and special pathology. 5th edition. Thieme, Stuttgart 2004. p. 233
  13. ↑ Müller, Höfler, Imhof, Holländer: Chapter 3, inflammation. In: Böcker, Denk, Heitz, Höfler, Kreipe, Moch: Pathology. 5th edition. Urban & Fischer, Munich 2012, p. 69
  14. ↑ Müller, Höfler, Imhof, Holländer: Chapter 3, inflammation. In: Böcker, Denk, Heitz, Höfler, Kreipe, Moch: Pathology. 5th edition. Urban & Fischer, Munich 2012, p. 69
    Hans-Hartmut Peter, Ursus-Nikolaus Riede: Chapter 5, Disorders of the preservation of individuality. In: Riede, Werner, Schäfer (Ed.): General and special pathology. 5th edition. Thieme, Stuttgart 2004, p. 231 ff
  15. ↑ Hans-Hartmut Peter, Ursus-Nikolaus Riede: Chapter 5, Disorders of the preservation of individuality. In: Riede, Werner, Schäfer (Ed.): General and special pathology. 5th edition. Thieme, Stuttgart 2004. p. 235
  16. ↑ Müller, Höfler, Imhof, Holländer: Chapter 3, inflammation. In: Böcker, Denk, Heitz, Höfler, Kreipe, Moch: Pathology. 5th edition. Urban & Fischer, Munich 2012, p. 69

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