In article <ralph.1141524010E at news.arizona.edu>,
Ralph M Bernstein <ralph at ccit.arizona.edu> wrote:
[question about distinction between cytokines and hormones]
>>OK, cytokines all act through a membrane bound receptor. I think that
>hormones are membrane soluable and go running in through the outer PM and
>get bound to an internal binding protein which can then escort or follow
>into the nucleus. That's a difference. Cytokines activate and work through
>this membrane bound receptor system and activate a signal transduction
>pathway-like PKCs ect. Hormones, when in the nucleus can act
>directly-binding and inducing transcription much more primarily. Also I
>think that hormones are usually planar-rings-hydrophobic so they go
>screaming through the PM, while cytokines are small proteins- many of them
>homologous to each other. Certainly, I WOULD call the immune system a
>specific organ, but thats me. You must also remember that many of the
>immune system's cytokines/lymphokines have been "stolen" from the
>developmental biologists, it's just that immunologists may have identified
>these molecules first. Example, IL-1 is very important in normal
>development, as well as playing a role in the mature individual not
>necessarily always as the endogenous pyrogen. Back to the first point, the
>main role of cytokines (in their immune system role) is to play a part in
>cell-to-cell communication.
>>>Ralph M. Bernstein
>Dept of Micro/Immuno
>University of Arizona
>Ph: 602 626 2585
>Fx: 602 626 2100
This is not true at all. While steroid hormones are membrane soluble and
act on receptors that are transcription factors, the peptide hormones
(growth hormone, ACTH, insulin) and amino acid derivatives (serotonin,
dopamine, epinephrine) all work through membrane-bound receptors.
In addition, a number of cytokines have been shown to be non-critical for
development. Knockouts of IL-2 and IL-4 have no developmental (or
immunological) defects.
However, I agree that the immune system is a true organ system, and it
seems to me that there is no real conceptual difference between cytokines
and other hormones.
BioKen
--
Ken Frauwirth (MiSTie #33025) _ _
frauwirt at mendel.berkeley.edu |_) * |/ (_ |\ |
Dept. of Molec. & Cell Bio. |_) | () |\ (_ | \|
Univ. of Cal., Berkeley Push the button...someone :(
