Monocytes are a special type of bone marrow-derived leukocytes commonly cultured in karyotyping procedure.
Karyotyping is a type of cytogenetic technique used commonly for observing chromosomes. Its objective is to investigate chromosomes for finding abnormalities associated with different genetic conditions.
It’s a traditional yet popular and versatile technique, scientists use for encountering various defects and to study chromosomes. Common sample types of karyotyping are amniotic fluid/chorionic villi, bone marrow and blood for prenatal, bone marrow and postnatal studies, respectively.
Experts use a blood sample frequently and hence named it as PBLC- peripheral blood leukocyte culture. In the present article, I will explain to you why the name PBLC is given and why only monocytes are targeted for it.
PBLC- peripheral blood leukocyte culture:
Karyotyping with blood often known as PLBL or peripheral blood leukocyte culture because of the use of only leukocytes in the process.
It’s a cell culture-based technique in which blood cells (leukocytes) are grown under strict aseptic conditions and using ready to use media or culture media. The aim of doing this is to grow metaphase cells.
In the next process, the metaphases are arrested and chromosomes are separated from the cells. G bands are performed and the microscope analyzes chromosomes. If you want to learn more about the entire process, you can read this article: steps and procedure of karyotyping.
The reason why cytogeneticist uses a blood sample is that it is available easily. Blood tissue comprises various types of cells that help our body to perform various functions.
Now the question is why only lymphocytes are practiced in karyotyping or PBLC? And what is the scene of monocytes? To answer this question we need to first learn about some basics of blood tissue.
Composition of blood:
The blood is a connective tissue that flows in every body part and provides hemoglobin. It’s made up of three common types of cells viz red blood cells, white blood cells and platelets known as erythrocytes, leukocytes and thrombocytes.
Red blood cells carry oxygen, white blood cells function in the immune system and induce immune responses and platelets perform in blood clotting.
The white blood cells are further divided into monocytes, lymphocytes, neutrophils, eosinophils, basophils and macrophages.
The percentage of blood cells are:
- Red blood cells: 40 to 45%
- White blood cells: 1%
- Lymphocytes: 30%
- Eosinophils: 2.3%
- Neutrophils: 62%
- Basophils: 0.4%
- Monocytes: 5.3%
The Karyotyping technique is a cell culture technique that requires diving cells. Leukocytes, a type of white blood cells are the only cells having a nucleus and are diving hence used in karyotyping.
Related article: What are the common Errors in Karyotyping Results?
Now coming to the question of the present article;
Why karyotyping is performed using blood monocytes only?
As we discussed above, monocytes are a type of leukocytes- white blood cells and used in investigating chromosomes, but the question here is why not other cell types such as neutrophils, basophils or eosinophils are used for this purpose. Some special characteristics of monocytes make them powerful enough to use in karyotyping.
- Monocytes are proliferative, bone marrow-derived leukocytes.
- 15 to 18micrometer in diameter (larger)
- Around 5 to 7% are leukocytes are monocytes.
- A single, bigger and unilobed nucleus.
The monocytes are cells actively participating in immune response and hence are rapidly diving (we will not discuss why so- it’s another topic to discuss).
Because of their proliferative characteristics, larger size and a substantial amount in blood favor it to use in karyotyping.
These are the reason a type of leukocyte- the monocytes are only used in PBLC or karyotying procedure.
Conclusively, i can say, blood samples are only be collected in the sodium heparin tubes in which the type of leukocytes- monocytes are only cultured to perform karyotyping. If you want to know why only sodium heparin tubes, you can read this article: Why only Sodium Heparin Tubes are used to collect Samples for Karyotyping?
Besides, researcher also need to optimize the experiment in order to get good results, for example, the use of pre-chilled slides, culturing within 24 and processing pre-aged slides.