lymphoblast
Meaning of lymphoblast: One word covering two quite different cells: an immature precursor in the marrow, and a mature cell swollen by activation.
Definition of lymphoblast
A lymphoblast is a large immature cell that develops into a mature lymphocyte. The same word is also used, confusingly, for a mature lymphocyte that has enlarged after meeting an antigen and is preparing to divide. Both are big cells with an open pale nucleus and prominent nucleoli, which is why the same name attached to both, though they occupy opposite ends of a cell's life.
How lymphoblast is built
- lymph/o Combining form · Latin lymph, lymphatic tissue
- -blast Suffix · Greek immature or forming cell
A medical term is read from its ending backwards: the suffix first, then the prefix, then the root. See all 223 word parts.
Why does one word cover two cells?
Appearance. Both are large, both have a nucleus with loose open chromatin and a visible nucleolus, and both have scant blue cytoplasm. Early microscopists named cells by what they saw, and the resemblance is genuine, because in both cases the cell is geared up for rapid division. The distinction lies entirely in history: one has never yet matured, the other has matured, been activated, and reverted to a growth state. Some writers use immunoblast or transformed lymphocyte for the second to avoid the ambiguity.
How do the two differ?
| Precursor lymphoblast | Activated lymphoblast | |
|---|---|---|
| Where found | Bone marrow and thymus | Lymph nodes, spleen, blood |
| Triggered by | Normal development | Contact with an antigen |
| Becomes | A naive lymphocyte | Effector and memory cells |
| Significance in blood | Abnormal, suggests leukemia | Normal in a viral illness |
Why does finding them in the blood matter?
That bottom row is the practical point. Precursor blasts belong in the marrow and should not circulate, so their presence in a blood sample raises the possibility of acute leukemia and prompts a marrow examination. Activated blasts in the blood are an ordinary finding during infections such as glandular fever, where they are described as atypical or reactive lymphocytes. Distinguishing an alarming finding from a routine one rests on this difference, and on the cell markers used to settle it.
What happens after activation?
An activated cell enlarges, restarts its division cycle, and produces a clone of identical daughters. Some become effector cells that secrete antibody or kill infected targets, and a smaller number become long-lived memory cells that respond faster on a second encounter. A B lymphocyte taking this path ends as an antibody-secreting plasma cell, whose appearance differs again, with an intensely blue cytoplasm and a nucleus pushed to one side.
Also known as
Used in a sentence
Numerous lymphoblasts were seen on the blood film, prompting urgent marrow sampling.
Good to know
Precursor blasts in a blood sample suggest acute leukemia and prompt marrow examination, whereas activated blasts circulating during a viral illness are an ordinary reactive finding.
Word origin
Where “lymphoblast” comes from
Combines the Latin lympha, meaning clear water, with the Greek blastos, meaning a sprout or germ.