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Many red blood cells with a single larger cell. The larger cell is pink with a purple region that fills nearly the entire cell. The purple region is labeled perforin-containing granules.
Natural killer cell with perforin-containing granules. (credit: modification of work by Rolstad B)

Monocytes

The largest of the white blood cells, monocytes have a nucleus that lacks lobes, and they also lack granules in the cytoplasm ( [link] ). Nevertheless, they are effective phagocytes, engulfing pathogens and apoptotic cells to help fight infection.

When monocytes leave the bloodstream and enter a specific body tissue, they differentiate into tissue-specific phagocytes called macrophages and dendritic cells . They are particularly important residents of lymphoid tissue, as well as nonlymphoid sites and organs. Macrophages and dendritic cells can reside in body tissues for significant lengths of time. Macrophages in specific body tissues develop characteristics suited to the particular tissue. Not only do they provide immune protection for the tissue in which they reside but they also support normal function of their neighboring tissue cells through the production of cytokines. Macrophages are given tissue-specific names, and a few examples of tissue-specific macrophages are listed in [link] . Dendritic cells are important sentinels residing in the skin and mucous membranes, which are portals of entry for many pathogens. Monocytes, macrophages, and dendritic cells are all highly phagocytic and important promoters of the immune response through their production and release of cytokines. These cells provide an essential bridge between innate and adaptive immune responses, as discussed in the next section as well as the next chapter.

Monocytes are large cells with a large purple nucleus. There is a cluster of them in a field of smaller red blood cells. A PMN is also visible with a dark, multi-lobed nucleus. Macrophages are large cells with a defined nucleus.
Monocytes are large, agranular white blood cells with a nucleus that lacks lobes. When monocytes leave the bloodstream, they differentiate and become macrophages with tissue-specific properties. (credit left: modification of work by Armed Forces Institute of Pathology; credit right: modification of work by Centers for Disease Control and Prevention)
Macrophages Found in Various Body Tissues
Tissue Macrophage
Brain and central nervous system Microglial cells
Liver Kupffer cells
Lungs Alveolar macrophages (dust cells)
Peritoneal cavity Peritoneal macrophages
  • Describe the signals that activate natural killer cells.
  • What is the difference between monocytes and macrophages?

Key concepts and summary

  • The formed elements of the blood include red blood cells ( erythrocytes ), white blood cells ( leukocytes ), and platelets (thrombocytes ). Of these, leukocytes are primarily involved in the immune response.
  • All formed elements originate in the bone marrow as stem cells (HSCs) that differentiate through hematopoiesis .
  • Granulocytes are leukocytes characterized by a lobed nucleus and granules in the cytoplasm. These include neutrophils (PMNs) , eosinophils , and basophils .
  • Neutrophils are the leukocytes found in the largest numbers in the bloodstream and they primarily fight bacterial infections.
  • Eosinophils target parasitic infections. Eosinophils and basophils are involved in allergic reactions. Both release histamine and other proinflammatory compounds from their granules upon stimulation.
  • Mast cells function similarly to basophils but can be found in tissues outside the bloodstream.
  • Natural killer ( NK ) cells are lymphocytes that recognize and kill abnormal or infected cells by releasing proteins that trigger apoptosis.
  • Monocytes are large, mononuclear leukocytes that circulate in the bloodstream. They may leave the bloodstream and take up residence in body tissues, where they differentiate and become tissue-specific macrophages and dendritic cells .

Matching

Match each cell type with its description.

___natural killer cell A. stains with basic dye methylene blue, has large amounts of histamine in granules, and facilitates allergic responses and inflammation
___basophil B. stains with acidic dye eosin, has histamine and major basic protein in granules, and facilitates responses to protozoa and helminths
___macrophage C. recognizes abnormal cells, binds to them, and releases perforin and granzyme molecules, which induce apoptosis
___eosinophil D. large agranular phagocyte that resides in tissues such as the brain and lungs

C, A, D, B

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Match each cellular defense with the infection it would most likely target.

___natural killer cell A. virus-infected cell
___neutrophil B. tapeworm in the intestines
___eosinophil C. bacteria in a skin lesion

A, C, B

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Fill in the blank

Platelets are also called ________.

thrombocytes

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The cell in the bone marrow that gives rise to all other blood cell types is the ________.

pluripotent hematopoietic stem cell (HSC)

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PMNs are another name for ________.

neutrophils

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Kupffer cells residing in the liver are a type of ________.

macrophage

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_____________ are similar to basophils, but reside in tissues rather than circulating in the blood.

mast cells

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Short answer

Explain the difference between plasma and the formed elements of the blood.

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List three ways that a neutrophil can destroy an infectious bacterium.

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Questions & Answers

Explain about enzyme transportation
Shahla Reply
Enzyme transportation
Shahla
what is the infectious disease process
Patience Reply
what are differences between endotoxins and exotoxins
sabote Reply
endo toxins work in the nuceus. i think
maxo
tell me if im right tho
maxo
Exotoxins are toxic substances secreted by bacteria and released outside the cell. Both gram positive and gram negative bacteria can produce and secrete exotoxins. Whereas Endotoxins are bacterial toxins consisting of lipids that are located within a cell. Only lysed gram negatives.
Abdi
Remebr the Lipid A portion of LPS is what's toxic.
Abdi
oh yeah. thanks
maxo
Your welcome :)
Abdi
How did you learn this?
maxo
For me personally the best book is 'microbiology made ridiculously simple'
Abdi
I got my basics from there and slowly added information from other sources.
Abdi
thats cool! yeah i like microbiology too! especially the molecular proteins theyre sooooooooooo cool!
maxo
what are the prokaryotic
Lungu Reply
prokaraytotic is a unicellular organizm that lacks membrane bound nucleus
Zaajid
and whats eukaryotic
abdiqani
eukaryotic cell are cell which contain anuclues and organells
Zaajid
eukaryotes are the cells that have organells which are protected by membranes
maxo
eukaryotic is are multicellular organisms which are open nucleus.
Serah
Explain on the Francisco reddi did to prove the theory of spontaneous generation
Diana Reply
what is parasite
Abdirizack Reply
parasite are organisms feeds on a host for food and survival.e.g round worm for animal, Dodder for plant parasites.
Serah
parasite are organisms that feeds on a host for food and survival.e.g round worm for animal and mistletoe for plant parasites.
Serah
parasite are organisms that feed on their host
Cylla
designing of aseptic area
Aashish Reply
I don't know
Abdirizack
what is rickettsia
DENNIS Reply
what is microbiology
Erasto
Is the science that works with microorganisms.
Rose
richettsa is small microorganisms that cause disease in human like typhus; they are like viruses that can grow only inside living cells, they're transmitted by mites, ticks or lices.
Rose
what is plasmid?
mavis
plasmid is extra chromosomal body present in bacteria...which have additional genetic functions example... antibiotic resistance genes....etc etc
Chaitanya
state the theory of spontaneous generation of micro oranisms and germ theory of disease
UKAMAKA Reply
what are the advantages of high note numerical aperture
Genius Reply
list if non flagellated pritozoa
Mepung Reply
Can someone that's understanding of the Kreb Cycle please explain & breakdown it down to me in the simplest way without giving me the dictionary version or Google version. Basically in there own words of knowledge....!
Kisha
ok
lucas
please can someone help explain positive and negative feedback in simple term
Gum
negative feedback is the arresting of reaction or reverse of the reaction according to the response and postive feed back is the direct response without reversing or arresting a reaction.
Greet
OK
umar
pls can someone explained Kinney stone in memorising in shot time
umar
what tyoebif microorganism will be killed by antibiotic trwatmeant
Mary Reply
I don't really don't understand aerobic respiration anaerobic respiration and fermentation. Can someone explain & breakdown this in the simplest way please.
Kisha
Anaerobic Respiration in which foodstuffs are partially oxidized, with the release of chemical energy, in a process not involving atmospheric oxygen, such as alcoholic fermentation, in which one of the end products is ethanol.
Muhammad
aerobic respiration A type of respiration in which foodstuffs are completely oxidized to carbon dioxide and water, with the release of chemical energy, in a process requiring atmospheric oxygen.
Muhammad
please can someone explain what pseudomonas species and biofilm is?
uju
Fermentation is the growth of cells or microorganisms in bioreactors (fermenters) to synthesize special products. Fermentation in biochemistry refers to the biodegradation of carbon compounds by cells or organisms under anaerobic (lack of oxygen) conditions.
Muhammad
Please under which conditions does pathogens become established in the human tissues and can cause diseases
Atambilla
please the life cycle of plasmodium parasite
mavis
who is John Needham
Mary Reply
John Needham is one of the researcher in microbiology. He also experimented when scientists did not believe animals could arise spontaneously ,but did believe microbes could.
Gum
okay is he late
Mary
by the way what are the list of courses offered by a newly admitted student for microbiology
Mary
Needham's experiments with beef gravy and infusions of plants material reinforced this idea.
Gum
what drugs are given to a person with Otis nerve problem(ear problem)
Gum Reply
good morning to you all.
Muhammad Reply
Dr.A.K.S.P.G. college Akbarpur Ambedkar Nagar
Rajan
Shailesh Vishwakarma BSc 1st year
Rajan

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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