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Revision as of 17:50, 27 May 2023

Immunoglobulin light chains

Lght chains form part of the b-cell receptor and may therefore be considered as a pan b-cell marker from late lymphoblasts until plasma cell differentiation. If abnormal cells express predomnantly kappa or lambda then clonality can be inferred. Absence of light chain is also abnormal and may incicate clonality.

normal function and expression

The antigen-recognising structure of the B-cell receptor is the immunoglobulin molecule formed from either kappa or lambda light chains in combination with immunoglobulin heavy chains. Normal mature b cells therefore express surface light chains as part of their B-cell receptor. During pro-B to pre-B cell development immunoglobulin genes rearrange to form unique structures Kappa or lambda light chains appear on the surface of immature B cells at later stages of development remaining expressed until plasma cell development when immunoglobulin is secreted so expression is within cytoplasmic secretory vesicles.

what is its diagnostic role

acquisition or loss of surface light-chain expression acquisition of surface light chains does not occur until late in b-precursor cell development so may be used to indicate developmental stage. Loss of surface expression indicates plasma cell differentiation.
clonality malignant b-cells arise from a single parent cell so express light chain of a single type either kappa or lambda - light chain restriction . in almost all cases there will be some normal cells present so light chains usually are a mixture of kappa and lambda. however when there is a malignant clone either kappa or lambda begins to predominate. Studies most frequently suggest that if the kappa to lambda ratio is 3 1 or 3 1 then the presence of a clonal population can be inferred although correlation with other markers is needed.
weak or absent light chain expression may be seen in DLBCL FL or CLL and more rarely in MCL or MZL. Overall around 10% of B-lymphoproliferative disorders do not express surface light chain.

summary tables

1. expression by acute leukaemias and by rare pro-b all poss early pre-b all poss pre-b all hi b all rare pro-t all rare mature-t all rare aml poss haemato-gones

expressed by late haematogones

2. expression by b-lymphoproliferative disorders hi cll hi pll** hi mcl hi fl hi hcl** hi hclv l hi mzl hi lpl poss pcs

@@ Line 1: / Line 1: @@
-tdt
+Immunoglobulin light chains
-tdt terminal deoxynucleotidyl transferase is expressed in the cell nucleus; detection therefore requires permeabilised cells. expression is expected in acute lymphoblastic leukaemias but is commonly also found in acute myeloid leukaemia. tdt is also strongly expressed by early haematogones and can help distinguish them from mature b cells; expression is lost as haematogones mature
+Lght chains form part of the b-cell receptor and may therefore be considered as a pan b-cell marker from late lymphoblasts until plasma cell differentiation. If abnormal cells express predomnantly kappa or lambda then clonality can be inferred. Absence of light chain is also abnormal and may incicate clonality.
-what is its normal function and expression   tdt acts during the v d j rearrangement of heavy chain of the t-cell receptor or b-cell receptor gene segments required for the formation of mature b and t cells in thymus or marrow. expression of tdt in normal cells is restricted to immature b-cells in bone marrow. in the t-lymphocyte lineage it is expressed by pre-t lymphoid cells and cortical thymocytes. in regenerative marrows tdt is consistently expressed on regenerative b lymphocytes haematogones which may represent a large proportion of cells in some cases particularly in children .
+normal function and expression
-what is its diagnostic role   the most useful attribute of tdt is its loss of expression by mature cells. *tdt is expressed by haematogones becoming lost as they mature *tdt is consistently expressed by acute lymphoblastic leukaemia 95 *tdt may be weakly expressed by burkitt lymphoma but is most often absent mature b-cell lymphomas should not express tdt although it is rarely described *tdt is expressed infrequently in aml mainly on less differentiated forms and those related to mds around 20
+The antigen-recognising structure of the B-cell receptor is the immunoglobulin molecule formed from either kappa or lambda light chains in combination with immunoglobulin heavy chains. Normal mature b cells therefore express surface light chains as part of their B-cell receptor. During pro-B to pre-B cell development immunoglobulin genes rearrange to form unique structures Kappa or lambda light chains appear on the surface of immature B cells at later stages of development remaining expressed until plasma cell development when immunoglobulin is secreted so expression is within cytoplasmic secretory vesicles.
+what is its diagnostic role
+*acquisition or loss of surface light-chain expression acquisition of surface light chains does not occur until late in b-precursor cell development so may be used to indicate developmental stage. Loss of surface expression indicates plasma cell differentiation.
+*clonality malignant b-cells arise from a single parent cell so express light chain of a single type either kappa or lambda - light chain restriction . in almost all cases there will be some normal cells present so light chains usually are a mixture of kappa and lambda. however when there is a malignant clone either kappa or lambda begins to predominate. Studies most frequently suggest that if the kappa to lambda ratio is 3 1 or 3 1 then the presence of a clonal population can be inferred although correlation with other markers is needed.
+*weak or absent light chain expression may be seen in DLBCL FL or CLL and more rarely in MCL or MZL. Overall around 10% of B-lymphoproliferative disorders do not express surface light chain.
 summary tables
-expression by acute leukaemias and by haematogones
+. expression by acute leukaemias and by
-hi  pro-b all
+rare pro-b all
-hi  early pre-b all
+poss  early pre-b all
-hi  pre-b all
+poss  pre-b all
-poss  b all
+hi  b all
-hi  pro-t all
+rare  pro-t all
-hi  mature-t all
+rare  mature-t all
-mod  aml
+rare  aml
-hi  haemato-gones
+poss  haemato-gones
-*  may be secondary or more primitive forms
+*  expressed by late haematogones
-expression by b-lymphoproliferative disorders
+. expression by b-lymphoproliferative disorders
-rare cll
+hi cll
-rare  pll
+hi  pll**
-rare  mcl
+hi  mcl
-rare  fl
+hi  fl
-rare  hcl
+hi  hcl**
-rare  hclv
+hi  hclv  l
-rare  mzl
+hi  mzl
-rare  lpl
+hi  lpl
-rare  pcs
+poss  pcs

Extra: Difference between revisions

From haematologyetc.co.uk

Revision as of 17:50, 27 May 2023